INTERNAL ORGANS OF GENERATION. 35 



Goat, and each is provided with a single conical, well-detached teat. The 

 latter animal has sometimes, in addition, two posterior rudimentary teats, 

 and the galactophorous sinus of each ordinary teat in this animal is very 

 large, the walls of the teat being thin ; it is capable of containing, in some 

 instances, nearly three ounces of milk. 



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 is denoted, externally, by a slight vertical de- 

 pression, and a trifling convexity corresponding to the teat. 



The mammae of this animal are scarcely perceptible while they are not 

 active ; but during lactation they form two series of well-developed emi- 

 nences, 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 conveyed 

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

 ^a certain period: this retention after a time distending the glands very 

 much, and putting the elastic envelope greatly on the stretch ; while the 

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

 becomes inordinate, it causes the animal uneasiness and pain ; and if 

 not relieved by natural or artificial means, it may occasion mischief. 

 The pressure of the envelope on the contained fluid in the majority 

 of cases overcomes the resistance of the sphincter at the end of the teat, 

 and relief is in this way afforded. 



CHAPTER III. 



Internal Organs of Generation. 



The internal ox formative organs of generation are contained within the 

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

 include with the external organs), icterus, 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 cavity, 

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

 which it embraces in a kind of semicircular cul-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 



