36 OBSTETRICAL ANATOMY. 



Pig. 



In the Pig the mammae are ten or twelve in number, disposed by 

 pairs in two parallel rows extending from the inguinal region to beneath 

 the thorax, and distinguished as inguinal, abdominal, and thoracic 

 mammae. They have not, as in the larger animals, any sinuses, the 

 lactiferous canals of each teat joining directly to form a variable number 

 of excretory ducts, which open at the free extremity of the teat by 

 from five to ten orifices. The limits of each gland are denoted, extern- 

 ally, by a slight vertical depression, and a trilling convexity correspond- 

 ing to the teat. 



The mammas of this animal are scarcely perceptible while they are 

 not active ; but during lactation they form two series of well-developed 

 eminences, divided on the middle line by a wide and deep furrow. 



Bitch. 

 In the Bitch there are eight to ten mammae, arranged as in the Pig. 

 When the latter number is present they are disposed on each side as 

 two pectoral, two abdominal, and one inguinal. 



The secretion of milk is a special function of the mammary glands, 

 and takes place in the caecal vesicles of the lobules. The fluid is con- 

 veyed from these into the lactiferous ducts and sinuses, where it is 

 stored until a certain period : this retention after a time distends the 

 glands very much, and puts the elastic envelope greatly on the stretch ; 

 while the teat also increases in size, length, and firmness. When this 

 distension becomes inordinate, it causes the animal uneasiness and 

 pain, and if not relieved by natural or artificial means it may occasion 

 mischief. In the majority of cases, the pressure of the envelope on the 

 contained fluid overcomes the resistance of the sphincter at the end of 

 the teat, and relief is afforded in this way. 



CHAPTEE III. 

 Internal Organs of Generation. 



The internal or formative organs of generation are contained within 

 the pelvis and abdomen, and comprise the vagina (which some writers 

 include with the external organs), uterus, Fallopian tubes, and ovaries. 



SECTION I.— THE VAGINA. 

 The Vagina is a musculo-membranous canal of variable dimensions, 

 with thin walls ; it extends almost horizontally within the pelvic cavit}^ 

 from the vulva posteriorly to the uterus anteriorly, the cervix or neck 

 of which it embraces in a kind of semicircular ciil-de-sac. The rectum 

 lies above it, and the bladder below ; on each side are the ureters and 

 the walls of the pelvis, and posteriorly it is surrounded by adipose and 

 loose connective tissue. When distended it is cylindrical in form, but 

 usually its sides are in contact. Its length is variable, of course, but 

 in a full-sized Mare it is about a foot long. It is maintained in position 

 anteriorly by folds of peritoneum, which attach it to the rectum above 

 and to the bladder beneath, the attachment to the rectum being accom- 

 plished through the medium of the loose connective tissue referred to. 

 But this tissue, which also unites it to the bladder, is here close and 



