488 THE ANATOMY OF THE HORSE 



THE PELVIS 



The cavity of the body known as the pelvis is situated beliind the 

 abdomen, with which it communicates freely, each being lined by a continua- 

 tion of the peritoneum. A ridge of bone (the brim of the pelvis) is the line 

 of demarcation anteriorly. The sacrum and os coccygis bound it superiorly, 

 the anus posteriorly, and the ossa innominata inferiorly and laterally. It 

 contains the bladder and rectum in both sexes, and in each the organs of 

 generation peculiar to it. 



THE BLADDER 



The bladder is a musculo-membranous bag destined to contain the urine 

 as it is gradually received from the ureters, which bring it down from the 

 kidneys. It lies in the middle of the pelvis, occupying also more or less of 

 the abdomen according to its condition in point of i-epletion or emptiness. 

 It is of an oval shape, with its posterior extremity somewhat more pointed 

 than the other, and called its neck. At this point it gives origin to the 

 xirethra, a canal for carrying off the urine. It receives the two ureters at 

 its superior surface, about an inch in front of the neck, where they pierce 

 the several coats in an oblique direction forming a complete valve, which 

 prevents the return of the urine, and so invisible that the presence of two 

 openings is scarcely ever suspected by the ordinary observer. Only about 

 one-third of the bladder is covered by the peritoneum, the remainder being 

 made up solely of the muscular and mucous coats, which compose all the 

 hollow viscera. It is retained in its place by the cellular membrane which 

 connects it with the lower walls of the pelvis, posteriorly by the urethra, 

 and by the folds of the peritoneum, which are continued from it to the 

 sides of the pelvis, and are called the broad ligaments of the bladder. 



THE ORGANS OF GENERATION, MALE AND 

 FEMALE 



The male organs of generation consist of the testes and their ducts, 

 the vasa deferentia, the latter conveying the semen to the urethra or to the 

 AX'siculse seminales, which ai-e oval bags connected with the upper surface 

 of the neck of the bladder. Here the seminal fiuid is stored up for use, 

 and when wanted is conveyed into the vagina by means of the external 

 organ or penis. The anatomy of the testicles is that which mainly concerns 

 the horse-master, as they are generally removed by operation. They are 

 contained within the scrotum, which is externally composed of skin, wrinkled 

 in the foal, but subsequently distended by the size and weight of its contents. 

 Lcncath this is a layer of a pale yellowish fibrous membrane called the 

 dartos, which envelops the testes and forms a separation between them. A 

 thin coat of cellular membrane alone separates this from the double serous 

 membrane, tlie tunica vaginalis, which almost entirely envelops each testis, 

 just as the pleura docs the lung. In tlie early stages of fcetal life the testes 



