244 OUTLINES OF EQUINE ANATOMY. 



puclic artery, whicli sends a brancli backwards along the 

 upper surface of the organ to meet the anterior hranch of 

 the internal pudic, which also gives off a branch backwards 

 to gain the artery of the bulb. Immediately investing 

 the surface of the urethra, situated in the inferior groove 

 of corpus cavernosum, is corpus spongiosum, a thin layer 

 consisting of erectile tissue analogous to that found in 

 the hard palate serving to connect the mucous membrane 

 to the bony palate. Thus it consists of a network of 

 elastic tissue, through which blood-vessels ramify, and 

 which sometimes presents venous sinuses. Posteriorly, 

 against the crura, it forms a small dilatation termed the 

 bulb, which is covered by erectores penis. Posteriorly 

 it forms a large prominent portion, glans penis, which, 

 under erection, assumes the shape of the extremity of a 

 trumpet. It completely covers the anterior portion of the 

 corpus cavernosum, and around its outer circumferent 

 margin is a row of glands, corona glanclis, which secrete a 

 sebaceous material. It is covered by a highly sensitive 

 mucous layer, and at its centre, inclined to the lower part, 

 presents a deep depression, into which the anterior extre- 

 mity of the urethral canal projects, and which secretes a 

 strong-smelling greyish matter, termed smegma preputii. 

 Prom one infero-lateral part of the corpus cavernosum to 

 the other, transverse, dark- coloured muscular fibres run 

 underneath the urethra and corpus spongiosum, forming 

 the accelerator urinae muscle, which runs from the glans 

 penis as far back as the erectors. Along its under surface 

 may be seen two bands, apparently of white fibrous tissue, 

 which may be traced as far as the lateral part of sphincter 

 ani. These are the retractores penis, composed of invo- 

 luntary muscular fibres. 



The penis as above described is inferiorly covered by 

 skin which communicates laterally with that covering the 

 thighs, superiorly with that ^^ortion extending towards the 

 anus over the sj)ace termed the perineum, and anteriorly 

 it spreads outwards and joins the posterior part of the 

 cuticular layer of the scrotum, and in front of this the outer 

 layer of the prepuce. The prepuce or foreskin is a circular 

 inversion of the skin inward to form mucous membrane. 

 Anteriorly it is continued forwards to form a raphe in the 

 neighbourhood of the umbilicus. The skin in this region 

 is very thin, and in most horses almost hairless. The 



