DAIRY FARMING DAIRYING. 81 



"The structure of the mammary glands can be studied to advantage by injecting 

 each teat and the arteries and veins with different colored injection masses. Each 

 gland is enveloped in an elastic, fibrous capsule or membrane, to which externally 

 the skin is loosely adherent; internally the fibers intermingle with those of the 

 gland from the opposite side and become prolonged upward as a suspensory 

 ligament. . . . 



"Above the teat is a large cavernous opening, the reservoir or milk cistern. This 

 cistern is divided by constrictions into pockets of various sizes, into which the larger 

 milk ducts empty. At the point of entrance of these ducts is a constriction due to a 

 sphincter muscle. These sphincters can not close the entire opening, but it seems 

 possible that they may partially do so, and this may thus account for the ('ondition 

 known to all dairymen as 'holding up the milk.' 



' ' The large ducts ramify in an irregular manner to all parts of the gland. They 

 subdivide into smaller ducts, and these in turn into smaller ones, until they terminate 

 in a simple duct with its alveolus or pocket. The large ducts anastomose ver\^ freely, 

 but do not in the smaller subdivisions. The canal in the teat, the reservoir, and ducts 

 are lined with columnar epithelium, but just what part the epithelial cells lining 

 these ducts have in the production of milk is not known. 



' ' The alveolus is the sacculated distension on the end of the minute milk duct. It 

 is the essential part of the gland. It is lined by a single layer of epithelial cells, 

 which are especially concerned in milk secretion. The cavity of the alveolus in the 

 cow is from -^jo to t^o of an inch in length, and from 0.13 to 0.08 of an inch in diam- 

 eter. The lining cells vary from almost a flattened form to a columnar form during 

 the different stages of rest and activity. 



"The mammary glands are abundantly supplied with blood. . . . The manunary 

 artery has 4 principal branches, 2 going to the posterior gland, 1 branch between 

 the glancis, with nearly all its subdivisions entering the anterior gland. There is 

 also a small branch for each rudimentary gland. The large branches subdivide 

 within the gland tissue. . . . The larger volume of blood passes forward through 

 the subcutaneous veins, thus bringing them into great prominence and giving rise to 

 the popular name of milk veins. These abdominal veins enter the thoracic cavity 

 just behind the sternum on each side of the cartilage, the point of entrance into the 

 body being known as the 'milk well.' As the blood may pass to the heart through 

 the posterior vessels as well as the anterior, it would seem that undue j^rominence is 

 attached to these veins in judging the milking qualities of cows. If a large volume 

 of blood should return by way of the posterior vessels, the abdominal veins \\ ill 

 appear less prominent. One of the factors tending to increase the size of these veins 

 is pressure upon the iliacs, as a gravid uterus. . . . 



"The nerve center controlling secretion has not been located, but it is supposed to 

 be in the spinal cord. It is possible that the will can exercise some influence, but 

 the evidence is not sufficiently clear to warrant drawing a positive conclusion." 



On the economy of heavy grain feeding of dairy govts, F. W. 



WoLL iind W. L. C'arlyle ( Tr7.sYV>/^s/// Sfa. Bpf. 1S9D^ pp. o'2-67). — 

 The proportion of grain feed to coarse fodder best adapted for the 

 economical production of milk and butter was studied in an experiment 

 with y lots of -J: cows each, lasting- 3 months. A ration consisting of 

 8 lbs. of a mixture of ground oats, ground corn, wheat bran, and old- 

 process linseed meal, 4 lbs. of mixed clover and timoth}^ hay, and 

 silage ad lih'd/mn. was fed to lot A during the tirst and third periods, 

 and to lot B during all 3 periods. During the second period lot A 

 received the same ration except that the amount of grain was increased 



