Bulletin 379 November, 1942
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
WILMON NEWELL, Director
CIRCULATORY SYSTEM OF THE
By R. B. BECKER and P. T. Dix ARNOLD
Fig. 1.-The network of veins on this udder of Fox's Jolly Girl 247588
is evidence of a hard-working udder. Four Register of Merit records by
this cow averaged 10,683 lbs. milk, 5.30% fat, and 567 Ibs. of butterfat.
Single copies free to Florida residents on request to
AGRICULTURAL EXPERIMENT STATION
EXECUTIVE STAFF BOARD OF CONTROL
John J. Tigert, M.A., LL.D., President of the H. P. Adair, Chairman, Jacksonville
University3 R. H. Gore, Fort Lauderdale
Wilmon Newell, D.Sc., Director3 N. B. Jordan, Quincy
Harold Mowry, M.S.A., Asso. Director T. T. Scott, Live Oak
L. O. Gratz, Ph.D., Asst. Dir., Research Thos. W. Bryant, Lakeland
W. M. Fifield, M.S., Asst. Dir., Admin.* J. T. Diamond Secretary, Tallahassee
J. Francis Cooper, M.S.A., Editors
Clyde Beale, A.B.J., Assistant Editors BRANCH STATIONS
Jefferson Thomas, Assistant Editor3
Ida Keeling Cresap, Librarian NORTH FLORIDA STATION, QUINCY
Ruby Newhall, Administrative Managers J. D. Warner, M.S., Agronomist in Charge
K. H. Graham, Business Managers R. R. Kincaid, Ph.D., Asso. Plant Pathologist
Claranelle Alderman, Accountant3 R. W. Wallace, B.S., Asso. Agronomist
J. H. Wallance, M.A., Asso. Agronomist
MAIN STATION, GAINESVILLE Elliott Whitehurst, B.S.A., Asst. An. Husb."
W. C. McCormick, B.S.A., Asst. An. Hush.
AGRONOMY Jesse Reeves, Asst. Agron., Tobacco
W. E. Stokes, M.S., Agronomist1 W. H. Chapman, M.S., Asst. Agron.4
W. A. Leukel, Ph.D., Agronomist3 CITRUS STATION, LAKE ALFRED
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Associates A. F. Camp, Ph.D., Horticulturist in Charge
W. A. Carver, Ph.D., Associate V. C. Jamison, Ph.D., Soils Chemist
Roy E. Blaser, M.S., Associate B. R. Fudge, Ph.D., Associate Chemist
G. B. Killinger, Ph.D., Associate W. L. Thompson, B.S., Associate Ento.
Fred A. Clark, B.S.A., Assistant F. F. Cowart, Ph.D., Asso. Horticulturist
W. W. Lawless, B.S., Asst. Horticulturist4
ANIMAL INDUSTRY R. K. Voorhees, Ph.D., Asso. Plant Path.
A. L. Shealy, D.V.M., An. Industrialist1 3 H. 0. Sterling, B.S., Asst. Hort.
R. B. Becker, Ph.D., Dairy Husbandmans T. W. Young, Ph.D., Asso. Hort., Coastal
E. L. Fouts, Ph.D., Dairy Technologists C. R. Stearns, Jr., B.S.A., Chemist
D. A. Sanders, D.V.M., Veterinarian EVERGLADES STA.. BELLE GLADE
M. W. Emmel, D.V.M., Veterinarian3
L. E. Swanson, D.V.M., Parasitologist' J. R. Neller, Ph.D., Biochemist in Charge
N. R. Mehrhof, M.Agr., Poultry Husb.3 J. W. Wilson, Sc.D., Entomologist
T. Freeman, Ph.D., Asso. in Dairy Mfg. F. D. Stevens, B.S.. Sugarcane Agron.
R. S. Glasscock, Ph.D., Asso. An. Husb. Thomas Bregger, Ph.D., Sugarcane
D. J. Smith, B.S.A., Asst. An. Husb.4 Physiologist
P. T. Dix Arnold, M.S.A., Asst. Dairy Hush.s G. R. Townsend Ph.D., Plant Pathologist
G. K. Davis, Ph.D., Tech. in An. Nutrition R. W. Kidder, M.S.., Asst. An. Hush.
L. E. Mull, M.S., Asst. in Dairy Tech.4 W. T. Forsee, Ph.D., Asso. Chemist
0. K. Moore. M.S., Asst. Poultry Hus. B. S. Clayton, B.S.C.E., Drainage Eng.-
C. B. Reeves, B.S., Asst. Dairy Tech. F. S. Andrews, Ph.D., Asso. Truck Hort.4
J. E. Pace, B.S., Asst. An. Husb. Roy A. Bair, Ph.D., Asst. Agron.
"E. C. Minnum, M.S., Asst. Truck Hort.
ECONOMICS, AGRICULTURAL SUB-TROPICAL STA., HOMESTEAD
C. V. Noble, Ph.D., Agr. Economist' Geo. D. Ruehle, Ph.D., Plant Path. in Charge
Zach Savage, M.S.A., Associate S. J. Lynch, B.S.A., Asst. Horticulturist
A. H. Spurlock, M.S.A., Associate E. M. Andersen. Ph.D., Asst. Hort.
Max E. Brunk. M.S.. Assistant
r OM.IC HOM W. CENT. FLA. STA., BROOKSVILLE
ECONOM S. HOME W. F. Ward, M.S., Asst. An. Hush. in Charge'
Ouida D. Abbott, Ph.D., Home Econ.1
Ruth 0. Townsend, R.N., Assistant RANGE CATTLE STA., ONA
R. B. French, Ph.D., Asso. Chemist W. G. Kirk, Ph.D., An. Hush. in Charge
ENTOMOL Y E. M. Hodges, Ph.D., Asso. Agron., Wauchula
ENTOMOLOGY Gilbert A. Tucker, B.S.A., Asst. An. Husb.4
J. R. Watson, A.M., Entomologist1 Floyd Eubanks, B.S.A., Asst. An. Husb.
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant FIELD STATIONS
G. H. Blackmon, M.S.A., Horticulturiat' M. N. Walker, Ph.D., Plant Path. in Charge4
A. L. Stahl, Ph.D., Associate K. W. Loucks. M.S., Asst. Plant Path.
F. S. Jamison, Ph.D., Truck Hort. E. E. Hartwig Ph.D., Asst. Agron. & Path.
R. J. Wilmot, M.S.A., Asst. Hort. Plant City
R. D. Dickey, M.S.A., Asst. Hort. A. N. Brooks, Ph.D., Plant Pathologist
J. Carlton Cain, B.S.A., Asst. Hort.4 Hastings
Victor F. Nettles, M.S.A., Asst. Hort. A. H. Eddins, Ph.D., Plant Pathologist
Byron E. Janes, Ph.D.. Asst. Hort. E. EddCubbin, Ph.D., Plant Pathologist
Fy. S. Lagassee, Ph.D., Asso. rt.Truck Hrt.
H. M. Sell, Ph.D., Asso. Hort.s Monticello
S. O. Hill, B.S., Entomologist' *
PLANT PATHOLOGY A. M. Phillips, B.S., Asst. Entomologist2
W. B. Tisdale, Ph.D., Plant Pathologist' s Bradenton
George F. Weber, Ph.D., Plant Path.8 Jos. R. Beckenbach, Ph.D., Truck Hort. in
Phares Decker, Ph.D., Asso. Plant Pathologist Charge
Erdman West, M.S., Mycologist E. G. Kelsheimer, Ph.D., Entomologist
Lillian E. Arnold, M.S., Asst. Botanist F. T. McLean, Ph.D., Horticulturist
A. L. Harrison, Ph.D., Asso. Plant Path.
SOILS David G. Kelbert, Asst. Plant Pathologist
R. V. Allison, Ph.D., Chemist'1 Sanford
Gaylord M. Volk, M.S., Chemist R.W. Ruprecht, Ph.D., Chemist in Charge,
F. B. Smith, Ph.D., Microbiologists Celery Investigations
C. E. Bell, Ph.D., Associate Chemist Jack Russell, M.S., Asst. Entomologist
J. Russell Henderson, M.S.A., Associate3
L. H. Rogers, Ph.D., Asso. Biochemist5 Lakeland
Richard A. Carrigan, B.S., Asso. Chemist E. S. Ellison, Meteorologist2 4
L. E. Ensminger, Ph.D., Asso. Soils Chem. Harry Armstrong, Asso. Meteorologist'
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Chemist 1 Head of Department.
Thos. Whitehead, Jr., M.S.A., Asst. In cooperation with U. S.
R. E. Caldwell, M.S.A., Soil Surveyor 3 Cooperative, other divisions, U. of F.
Olaf C. Olson, B.S., Soil Surveyor On leave.
CIRCULATORY SYSTEM OF THE
By R. B. BECKER and P. T. DIx ARNOLD
Review of Literature ...................................... ........... 4
Investigation of Veins of the Cow's Udder .................. ....... 9
Other Observations ---............. .... ... ........... ........... ....... 14
Discussion of Results ................ .. .... .......... --.----------.... ---..... .. 15
Sum m ary and Conclusions ..................................... ..... .............. 16
Literature Cited ........................ ....................... ... ........... ...... 17
An understanding of the circulation in the udder of the cow
would facilitate research techniques dealing with secretion,
pathology, medication, and surgery of the mammary tissues.
The circulatory system of the udder has been the subject of in-
vestigation for three-quarters of a century. Most of the early
studies were casual rather than detailed, and as a result some
confusion has occurred in the literature concerning the direction
of drainage of blood from the udder. Also, various names have
been applied to the blood vessels of the udder. In this report,
the specific name used by an author will be cited.
Blood enters the udder by way of the external pudic (mam-
mary) artery through the inguinal canal. The arteries branch
and rebranch within the udder, ultimately forming the capillaries,
which vessels in turn unite to form the large veins that enter
the mammary venous plexus (venous circle) at the base of the
udder. The mammary venous plexus consists of the two major
veins which unite the external pudic with the subcutaneous
abdominal veins on the corresponding sides. These are joined
by anastomoses of major branch veins in the posterior and an-
terior parts of the udder. The rear anastomotic crossing usually
occurs just anterior to the supramammary lymph glands. The
anterior anastomosis is less prominent and may be located an-
terior to or in the forward portion of the fore udder. The sub-
cutaneous abdominal veins drain part of this blood forward
along the belly wall. A part is removed dorsally in the external
pudic (middle mammary) veins through the inguinal canal.
Some authors have stated that part of the venous blood leaves
the udder via the perineal (posterior mammary) veins in the
region of the escutcheon. The latter point, however, is one which
this report debates. The location of these blood vessels is shown
in Figures 2, 3, 4, and 5.
4 Florida Agricultural Experiment Station
The study of venous outflow reported herein was conducted
incidentally over a period of 23 years, as udders were obtainable
for the investigation.
Fig. 2.-Blood and lymph vessels passing from the udder upward through
the inguinal canals of the cow Nora Romp's Carnation 359409, show that
variations occur commonly in the blood vessel pattern. These vessels from
the left and right halves of the udder respectively are: (a) external pudic
or middle mammary vein, (b) mammary artery, (c) two lymph vessels from
the left supramammary lymph gland, (d) branched external pudic or middle
mammary vein, (e) mammary artery, and (f) one vessel from the right
supramammary lymph gland. This cow had a Register of Merit record of
12,225 lbs. milk, 5.36% fat, and 655 lbs. of butterfat in 365 days.
REVIEW OF LITERATURE
An early study of the cow's udder was published in 1868 by
FUrstenberg (6)1. He stated that the external pudic vein and
the subcutaneous abdominal vein originate from Poupart's
"Bande," since called the mammary venous plexus or udder cir-
cle, in the upper surface of the udder. He recognized a large
1 Italic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.
Circulatory System of the Cow's Udder 5
Fig. 3.-This dorsal view of the udder of Creole's Lassie Sue 306835
shows (a) a single large lymph vessel from the supramammary lymph
glands, the points at which the (b) mammary arteries and (c) external
pudic or middle mammary veins enter the glands, and (d) the subcutaneous
abdominal veins. The perineal (posterior mammary) veins enter approxi-
mately at the points (e). Distended with blood and lymph, the positions
of valves in the lymph vessel and veins can be seen. The vessels were tied
off, severed high in the inguinal region, and laid forward on paper to show
their point of origin in the udder. This cow had a Register of Merit record
of 9,579 lbs. milk, 4.92% fat, and 471 Ibs. of butterfat in 365 days.
6 Florida Agricultural Experiment Station
vein close to the supramammary lymph glands as a branch drain-
ing into the external pudic vein.
Plumb (13), at the Indiana station, followed Fiirstenberg in
stating that two pairs of veins drain the mammary gland. Bit-
ting (2) described these major veins somewhat in detail, and
mentioned that: "The only thing that determines the direction
of the blood is position of valves in the vessels." He stated fur-
ther that the volume of blood passing forward through the
subcutaneous abdominal veins gave them their great prominence.
Bitting agreed with Plumb that two pairs of veins drained venous
blood from the udder. As early as 1903 Riederer (14) mentioned
that valves in the veins of the cow's teat prevented their complete
injection with a prepared fluid.
The textbook by the French veterinarian Moussu, translated
in 1905 by Dollar (11), mentioned two pairs of efferent veins
from the udder. One pair was called the anterior sub-abdominal,
the other was mentioned as accompanying the mammary ar-
teries. Rubeli (15), in both words and illustration, indicated
only two pairs of efferent veins, the Vena cava caud. and the
Vena subcutanea abdominis. Zwart (25) stated that the Vena
pudenda external is not the only outlet, but that blood assembled
from the Ramus basalis cranialis and Ramus mammaricus cran-
ialis flows through the vessel which continues forward under
the skin and is called the Vena mammarica.
Graves (8) and Simms demonstrated in 1916 that ligation of
one, and later both, of the subcutaneous abdominal veins did not
cause cessation of milk production. Graves stated: "This ex-
periment shows that the posterior mammary veins are capable
of carrying all the blood away from the udder." This has been
interpreted to indicate drainage of blood outward by two pairs
of veins, although not mentioned specifically.
The Swedish author Wall, as translated by Crocker (22) in
1918, ascribed the outflow of venous blood to the subcutaneous
abdominal and external pudic veins.
In contrast to writers who ascribed efferent flow to two pairs
of veins, a number of authors described three pairs of efferent
veins, adding the posterior mammary or perineal veins, which
ultimately become branches of the internal pudic veins, as the
third pair. The first of these publications was Nelke's inaugural
dissertation (12) investigating the possible cause of milk fever
in cows. He mentioned that the ascent of the branch going to
the internal pudic vein must take the blood from the udder
Circulatory System of the Cow's Udder 7
around the pelvic arch into the pelvis. Nevertheless, he observed
in 1898 to 1900, that injections of the vascular system of the
udder could be accomplished best when attempted from the
proximal end of the inflowing arteries, or near the periphereal
end of the veins because of the valves.
Sisson (16) stated that the veins form a circle at the base of
the udder from which the blood is drained by three trunks, viz.,
the very large subcutaneous abdominal, the external pudic, and
the perineal veins. Ernst, Mohler and Eichhorn (5) ascribed
the major outflow of venous blood from the udder to the external
pudic veins and subcutaneous veins, or "milk veins," and also
included the perineal veins as avenues of outflow. Monvoisin
(10) agreed with Sisson in the main as to the vein pattern and
outflow of venous blood. Zeitzschmann (23, 24), who contributed
to the text by Grimmer (9), likewise indicated the same three
pairs of veins as outlets for venous blood. Grossman's revision
of Sisson's "Veterinary Anatomy" (17) was practically a copy
of the previous edition, as regards udder venation.
Glittli's inaugural dissertation (7) was a detailed study in
which he recognized the fact that he differed with Fiirstenberg
(6) and Zwart (25), when he ascribed three outlets for venous
blood on each side of the udder. He stated that the large branch
veins from the secretary tissue lack valves, and that by this
means as well as by anastomoses between the veins, the blood
may leave the udder by any avenue. His conclusions were based
on examination of seven udders. Turner (20, 21) used the illus-
tration by Glattli (7) and followed his description of venous
flow. The presence of valves must have been noticed by Gliittli
in the larger veins, but these were not mentioned by either
author in this connection.
The most detailed anatomical study of the cow's udder con-
ducted in the United States was done in 1928 by Emmerson (4),
who injected the veins with a celluloid preparation. Since some
pressure must be applied in accomplishing complete injection, it
is possible that the thin tissues of the valves may have been
damaged. He observed anastomotic arcs between both deep and
superficial branch veins draining the udder. Emmerson believed
that the external pudic veins, which sometimes are called the
middle mammary veins, are the most constant channel by which
blood returns from the udder to the heart. The subcutaneous
abdominal veins with their branches may vary greatly in size.
He stated that the perineal vein or veins is subject to great
8 Florida Agricultural Experiment Station
variations, but made no mention of valves therein. Emmerson
made the observation that: "Very rarely, a small venous radicle
may leave the lateral surface of the udder over the reflection of
the skin from the medial surface of the thigh . and join the
saphenous vein of its respective side returning some blood to the
heart through this channel."
Ellenberger and Baum (3) copied Zeitzschmann (23) and
stated that the venous blood had three avenues outward, namely
the V. pudenda int., V. pudenda ext., and V. subcutanea abdom-
inis, the latter two being the larger ones.
A preliminary report by the senior author (1) summarized the
findings from 10 udders examined between 1923 and 1937. The
perineal veins (branches of the internal pudic veins) were ex-
amined in seven of these udders, and in every instance valves
showed the direction of flow of venous blood into the udder from
the adjacent region. From these observations it was concluded
that: . the posterior mammary or internal pudic vein no
longer can be considered as an efferent vein.
"Other observations were that sometimes there may be a
double anastomosis of the mammary vein in the rear of the
udder. The vein pattern varies widely. A variable number of
valves occur in the mammary venous plexus, which divide the
direction of venous flow between the subcutaneous abdominal
veins anteriorly, and the external pudic or middle mammary
veins upward from the rear quarters."
Swett (19) questioned whether venous blood entered or left
the udder by way of the perineal branch of the internal pudic
veins. His investigations concerning this point were summar-
ized as follows:
"The direction of flow of blood in the veins is controlled by
valves. Eight udders were used in studying the valves in the
perineal veins. In two cases molds of the valves were prepared
by injecting liquid rubber (latex) and making dissections after
the latex had hardened. In the other six cases the valves were
studied by splitting the veins longitudinally while the tissues
were fresh. In one case no valves were found except in close
proximity to the vulva. This pointed toward the vulva. In all
of the other seven cases, however, valves were found at various
locations below the region of the vulva-all pointing toward the
udder-which showed that the direction of flow was toward the
Circulatory System of the Cow's Udder 9
INVESTIGATION OF VEINS OF THE COW'S UDDER
Large and numerous veins on an udder popularly are asso-
ciated with heavy milk production in dairy cows. Fox's Jolly
Girl 247588 at Oklahoma A. & M. College was a good illustration
of such a cow. The veining on her udder is shown in Figure 1.
The major blood vessels serving the udder through the inguinal
canal are illustrated by the udder of Nora Romp's Carnation
359409, shown in Figure 2. This cow also was used in the earlier
part of the investigation of udder venation at the Oklahoma
An understanding of the udder anatomy in relation to the
circulatory system may be gained from Figure 3, which shows
the dorsal view of the udder of Creole's Lassie Sue 306835, at
the Florida station. In this illustration only the approximate
location of the posterior mammary perineall) veins can be indi-
cated, as these vessels were not ligated before severing the udder
from the body.
The present interest in this study traces to 1920, when a group
of graduate students under the late Dr. A. C. McCandlish were
unable to demonstrate the perineal branches of the internal pudic
veins as efferent veins in an udder obtained from a dairy heifer.
Contrary to the textbooks available (5, 16), valves found in this
vein directed flow of blood toward the udder. Furthermore, F.
Smith (18) had stated:
"In the veins valves are found . The valves look toward
the heart, and supply a simple and essential means of insuring
the return flow along the veins to the heart. In certain places
the veins have no valves, such as the large veins entering the
heart, those of the bones, the abdominal veins, and the veins of
the foot and brain."
Bitting (2) also had stated: "The only thing that determines
the direction of blood is position of valves in the vessels." Gliittli
(7) mentioned that the large veins from the secretary tissue of
the udder lack valves.
Since the flow of blood in the veins usually is governed by
valves, the valves were located, and their direction determined,
by one or both of two means. Examinations of udders in this
investigation were made in most instances by applying slight
pressure externally to observe the movement of blood within a
vein. Blood passes freely in the direction of natural flow; how-
ever, it stops when a valve fills with blood pressed from the
opposite direction. This method was used when working with
10 Florida Agricultural Experiment Station
freshly dissected specimens, to determine both the number of
valves and their direction in a vein. With older specimens, it
was necessary to section the veins longitudinally to see the valves
and the direction of flow which they govern.
Ten udders were examined at the Kansas, Oklahoma, and Flor-
ida Agricultural Experiment Stations between 1923 and 1937,
and the findings summarized in a preliminary report (1). The
conditions under which some of these udders were obtained
failed to provide much of the perineal veins for examination.
Seven additional udders have been obtained from registered
Jersey cows during 1938 to 1942, particularly to examine the
valves in the portion of the perineal (posterior mammary) veins
near the udder. Sketches indicating the valves ascertained and
the direction of flow of venous blood governed by them, are
shown in Figures 4 and 5.
The numbers and locations of valves in the mammary venous
plexus (venous circle) and the other veins examined will be
described case by case.
Cow No. 214.-Three valves on the left side of the mammary
venous plexus, and two on the right, directed blood flow poster-
iorly to the base of the external pudic veins. A valve near the
base of each external pudic vein pointed flow dorsally through
the inguinal canal. In eight inches of the perineal veins obtained,
four valves pointed flow in each toward the udder. No valves
occurred in the posterior anastomotic crossing. Three valves
were noted in major branch veins entering the mammary venous
plexus, and one in a secondary branch vein in a fore quarter of
Cow No. 264.-On each side of the mammary venous plexus
two valves pointed toward the subcutaneous abdominal veins,
and three posteriorly toward the external pudic veins. The an-
terior anastomotic crossing had one valve at each end pointing
flow laterally and forward. No valves occurred in the rear
anastomotic crossing. A single valve pointed toward the udder
in the short section obtained of each perineal vein. Two valves
were noted in major branches flowing into the veins which enter
the subcutaneous abdominal veins.
Cow No. 343.-On each side of the mammary venous plexus
two valves pointed toward the subcutaneous abdominal veins,
and three backward toward the external pudic veins. No valves
occurred in the rear anastomotic crossing between the external
pudic veins. The left perineal vein had two, and the right three,
No. 24 No 264
No. 343 No. 520
-9-- -I J
Fig. 4.-Graphic representation of location of valves and direction of
flow of venous blood in veins of the udders of four cows-Nos. 214, 264, 343,
and 520. Legend: (a) subcutaneous abdominal veins emerging from anterior
border of the udder, (b) anterior anastomotic crossing, (c) large branch
veins emerging from udder, (d) suspensory ligament, (e) external pudic'or
middle mammary veins draining dorsally through the inguinal canals, (f)
rear anastomotic crossing, (g) perineal vein or veins which extend backward
and upward in the escutcheon and join the internal pudic vein. The number
and location of all valves found, and direction of venous flow which they
govern, are indicated by their insertion within these veins. Branch veins
are indicated only where prominent on the dorsal surface of the udder, and
examined for presence of valves. Bitting (2) found 14 to 17 large veins
entering the mammary venous plexus.
--a I V--Q
y- --4 e
No. 546 No. 60o?
Fig. 5.-Graphic representation of location of valves and direction of
flow of venous blood in veins in the udders of three cows-Nos. 532, 546,
and 602. Note the few valves in the veins of No. 602 as compared with
those of No. 546. Legend: (a) subcutaneous abdominal veins from anterior
border of the udder, (c) large branch veins emerging from udder, (d)
suspensory ligament, (e) external pudic or middle mammary veins draining
dorsally through the inguinal canals, (f) rear anastomotic crossing, and (g)
perineal veins which extend backward and upward in the escutcheon and
join the internal pudic vein. The number and location of all valves found,
and direction of venous flow governed by them, are indicated by their inser-
tion within these veins. No two udders are exactly alike in the location and
numbers of valves in the mammary venous plexus (venous circle).
Circulatory System of the Cow's Udder 13
valves all pointing flow into the rear anastomotic crossing, thence
to the external pudic veins.
Cow No. 520.-One valve directed flow anteriorly to the left
subcutaneous abdominal vein, and on each side two valves pointed
flow posteriorly to the external pudic veins. One valve directed
flow dorsally in the left, and two in the right, external pudic
veins. In the rear anastomotic crossing one valve pointed left
and two toward the right external pudic vein. A single perineal
vein contained one valve directing flow of venous blood into the
rear anastomotic crossing.
Cow No. 532.-Two valves directed flow forward in the mam-
mary venous plexus to the left subcutaneous abdominal vein, and
three posteriorly behind them. A single valve on the right side
of the plexus pointed posteriorly. One valve pointed to the left
and two to the right in the rear anastomotic crossing between
the external pudic veins. One valve directed flow dorsally in the
base of the left external pudic vein, but no valve was noted in
either of two external pudic veins ascending toward the right
inguinal canal. Two valves in the left perineal vein and one in
the right directed flow into the rear anastomotic crossing. Dor-
sally, these veins were united for 6.5 inches, in which extent
three more valves pointed udder-ward. Branching again below
the vulva, one valve pointed ventrally and one dorsally in the
left branch. Two valves were noted in major branch veins enter-
ing the mammary venous plexus in the left rear, and another
in the right fore quarter of the udder.
Cow No. 546.-Two valves on each side of the mammary ven-
ous plexus directed flow of blood anteriorly into the subcutaneous
abdominal veins. Four valves on the left and three on the right
side guided the flow posteriorly in the mammary venous plexus
toward the external pudic veins. One valve near the base in
each external pudic vein directed flow dorsally. Only one valve
in the right side of the posterior anastomotic crossing directed
venous blood toward the external pudic vein on that side. Two
valves in the left perineal vein and one in the right directed flow
of blood into the posterior anastomotic crossing. A branch con-
nected these two veins at a slight distance above the udder.
Cow No. 602.-No valves directed venous flow anteriorly on
either side of the mammary venous plexus toward the subcutane-
ous abdominal veins. One valve on the left and two on the right
directed flow posteriorly toward the base of the external pudic
14 Florida Agricultural Experiment Station
veins. A valve near the base in each external pudic vein pointed
flow dorsally from the udder. Three valves in the rear anastomo-
tic crossing directed venous flow toward the right external
pudic vein. One valve in the perineal vein directed blood into
the rear anastomotic crossing in the udder. Above this valve
an anastomotic arc occurred outside of the udder in the single
perineal vein, and a single valve near the vulva directed flow
dorsally. A valve was found at the junction of a major branch
vein entering the rear anastomotic crossing.
This udder was one of those in which valves were observed
by movement of blood under slight pressure, after which the
veins were opened longitudinally, and each valve verified by
The blood vessel pattern may vary widely from udder to udder,
just as fingerprints differ between one person and another. Wide
variations were observed in the numbers and locations of valves
in major veins of the udders studied. Ordinarily, one or two
valves direct venous flow forward into the subcutaneous ab-
dominal veins, but in certain instances there were no valves
in this location. No valves were present in the rear anastomotic
crossing in one-half of the cases, yet from one to three valves
occurred there in the other udders.
Swett (19) observed valves directing flow into the udder from
the proximal end of the perineal veins in seven out of eight
udders, and no valves there in the other instance to prevent such
direction of flow. In the latter instance, direction of flow would
depend entirely upon the pressure existing within the vessel.
In the preliminary report (1), seven udders had valves directing
flow from the perineal veins toward the mammary venous plexus
in the udder. An insufficient length of the perineal veins was
obtained in three other specimens studied to make this de-
termination. In the present report of seven udders obtained
especially to observe the perineal veins, valves were found in
them directing flow of venous blood udder-ward in each instance.
Thus 21 out of 22 udders, where the investigators observed this
point, had valves in the perineal veins directing blood flow into
the udder, while venous blood in the single exception observed
by Swett could flow in either direction, depending on the state
of pressure within the vascular system.
Although no special attention was given to observe valves in
the major veins draining the udder area, yet valves were seen
Circulatory System of the Cow's Udder 15
in the udders of Cows No. 214, 264, 532, and 602 which directed
flow into the mammary venous plexus or venous circle. This
observation does not support the view of Glittli (7) concerning
absence of valves in this area, but tends to support the conclu-
sions of Nelke (12) and Riederer (14).
Concerning the anterior anastomotic crossing of the mammary
venous plexus, little uniformity was observed. From casual ex-
amination on the anterior dorsal surface of the udder, such a
crossing could be traced in the udder of Cows No. 214 and No.
343. Such crossing was not in evidence on the surface of No.
602's udder, although it may have existed deeper in the organ.
The venous connection between the right and left sides of the
udder was definitely less prominent in the anterior than in the
posterior part of the udder. There, the rear anastomotic cross-
ing between the bases of the external pudic veins is a prominent
vessel of good diameter.
No measurements were taken of the diameter of any of the
veins observed. From casual observation, the perineal veins were
always of smaller diameter than the rear anastomotic crossing
at the points of entrance.
DISCUSSION OF RESULTS
The present work, the preliminary report (1), and the detailed
investigations of udder circulation conducted by Swett (19) sup-
port the early work of Fiirstenberg (6) and his followers which
found that generally only two pairs of veins drain blood from
the udder. Emmerson (4) indicated that very rarely venous
outflow may be by a superficial vein crossing over from the
surface of the udder to the saphenous vein of the thigh.
The small size of the perineal veins was pointed out, as com-
pared with the size of the major veins of the udder. The fact
that venous blood in the perineal veins passes through such a
short route within the udder from the escutcheon region to the
external pudic veins probably would preclude its use for medica-
tion of the udder by intra-vascular injection.
The great variations in valve pattern in the veins of the udder
render direction of circulation subject to differentials in blood
pressure within the vascular system. Blood entering the mam-
mary venous plexus at several points may flow in either direc-
tion, depending upon the state of pressure within the vascular
system at the time.
16 Florida Agricultural Experiment Station
SUMMARY AND CONCLUSIONS
The branches of the internal pudic veins known as the perineal
veins carry venous blood into the mammary venous plexus in
the udder. Valves in 21 out of 22 cases observed closely are
the basis for this conclusion. The twenty-second case had no
valves in these veins, hence flow within them would be in the
direction of least pressure at the time.
The anastomotic crossing between the left and right sides of
the mammary venous plexus (venous circle) was defined less
clearly in the anterior part of the udder than that found com-
monly in the posterior part.
Valves were observed in some of the larger veins flowing from
the glandular region of the udder into the mammary venous
Emmerson has pointed out that in rare instances some venous
blood from the udder may flow out via the saphenous vein of
the thigh through a small superficial crossing.
Several associates have aided or verified the observations with the
various udders examined. Among these have been Dr. J. H. Burt, P. C.
McGilliard, Dr. D. A. Sanders, C. R. Dawson, Elizabeth J. Becker, and
others. One photograph was taken by J. R. Greenman. Franklin Branan
drew the illustrations for Figures 4 and 5. W. W. Swett made certain
Circulatory System of the Cow's Udder 17
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