364 SPLANCHNOLOGY. 



ment of the recently-born animal. In the young female, as in 

 the male, they are rudimentary, becoming developed in the 

 former at puberty,, or when the female is fit for reproduction. 

 During utero-gestation they gradually enlarge, and at parturi- 

 tion reach their greatest activity. When the period of suckling 

 terminates, they shrink, returning almost to their original state. 



In the mare, these glands are two in number, and placed, side 

 by side, in the inguinal region, between the thighs and under 

 the pubis, having the same relative position in the female as the 

 scrotum has in the male. In full activity, they present two 

 hemispherical masses, separated b}^ a shallow fissure, each half 

 presenting in its centre a nipple, teat, or mammary process, 

 pierced at its free extremity by numerous orifices for the passage 

 of the milk. The mammae are supported by an outer covering, 

 a continuation of the common integument, and by numerous 

 short elastic plates, similar to the suspensory ligament of the 

 male sheath, derived from the elastic abdominal fascia. The 

 outer tunic of integument is soft, black, and covered with fine 

 downy hair, which disappears towards the teat. Below this is a 

 thin elastic covering which blends with the elastic plates descend- 

 ing from the abdominal fascia. Besides supporting the gland, it 

 sends into its substance several prolongations, which form 

 partitions between the principal lobes. 



The interior of a mamma is made up of yellow glandular 

 tissue, consisting of numerous lobes, united by cellular tissue. 

 Each of these is again made up of small lobules, composed of 

 minute ducts and numerous small cells, or acini, in which the 

 milk is secreted and conveyed to the ducts, which unite to form 

 a common excretory duct for each lobe the ductus lactiferus, or 

 galactophorus. These increase in size, and by repeated union 

 converge to the centre of the gland, where they terminate in 

 dilated cavities the lactiferous sinuses, which vary in number, 

 and freely communicate with each other. From these proceed a 

 number of distinct canals, which run in a straight course to the 

 free extremity of the teat, where they terminate in a cribriform 

 manner, and by contracted orifices. The internal surface of this 

 excretory apparatus is lined by a fine mucous membrane, clothed 

 with columnar epithelium. 



The mucous membrane of the ducts is surrounded by a layer 

 of muscular fibre, which acts involuntarily as a sphincter, and 

 retains the milk, being assisted by a thin layer surrounding the 



