560 OPERATIONS ON THE GENITO-tJRINAKY APPARATUS. 



below the anus, but downwai'd and on the sides, is is covered with 

 short hau\ Below the skin are foimd the two principal layers of 

 aponeurotic covering, divided into the superficial and the deep. 

 The former, of fibro-elastic texture, is the continuation of the dar- 

 tos, and covers the perineal region, thinning down as it nears the 

 anus, to disappear at the sphincter ani. Its most superficial fibres 

 give attachment to a subcutaneous muscular fasiculus, which 

 from the spHneter ani runs downward to lose itself about three 

 inches below. The latter j)lane, or deep aponeurosis is formed of 

 white inextensible fibrous tissues. Intimately adherent by its 

 external face to the superficial layer, it covers and unites with the 

 accelerator urinae, and the ischio-cavernous muscles, as well as 

 with the suspensor and retractor ligaments of the penis. It then 

 passes between the ischio-cavernous and the semi-membranosus, 

 to attach itself above on the ischial tuberosity and become lost 

 downward on the thighs. Some of its fibres directly surround 

 the fixed portion of penis, and join the aponeurosis common to 

 all the muscles of the flat of the thigh. 



The sus23ensor and retractor of the penis form, in the upper 

 perineal region, that is, from the anus to the ischial arch, an ex- 

 pansion of sufficient width to form a true anatomical layer. Below 

 this they represent bands about half an inch wide, situated on the 

 median line, and covering the accelerator muscle. They are 

 formed of white muscular fibres. The blood-vessels and nerves 

 of this region, with the other parts pertaining to the anatomy of 

 the urethra, have already been considered. 



The pecuUarity that belongs to the penis of ruminants must 

 not be overlooked, when the question of urethrotomy in these 

 animals is under discussion. Their penis is very long and thin, and 

 is surrounded in the perineal region by a complete aponeurotic 

 sheath, and on a level with the pubis it has two curvatures, which 

 give to the organ the form of an S. On a level with the second 

 curvature it gives attachment to the suspensory ligaments. The 

 free portion of the organ is elongated, strongly fihform, and 

 covered by a fine, rosy mucous membrane. The peculiarities 

 possessed by the penis of the horse do not exist in cattle. 



The operation of urethrotomy is classified and designated with 

 reference to the part of the urethra, which is to be divided, and 

 this is of course determined by the location of the body to be re- 

 moved, making the designations principally regional; and it is 



