BY W. J. McKAY. 965 



opposite side in the mid-line below, and together they are pro- 

 longed forward, giving off tendons of insertion to the costo- 

 transverse processes. Before reaching the anus they diverge, 

 enclosing a space in which is seen the retractor cloacae, and 

 running forward they are inserted on the last rib, becoming 

 continuous with the pretrahentes costarum. The layer of muscle 

 appears to be on the same plane as the internal oblique stratum. 



On reflecting this layer we come on the transversus penis and 

 nexor caudse profundus. The latter muscle is composed of a 

 number of bundles springing from the costo-transverse processes ; 

 those run forward, and are inserted on the more anterior pro- 

 cesses. The transversus penis is a well-marked sheet of muscle ; the 

 bundles arise from the hypapophyses, and run inwards and back- 

 wards, being attached to the penis, while they meet the bundle of 

 the opposite side in the mid-line below. The nerves lie external 

 to this layer. 



On reflecting the transversus penis we find the retractor 

 cloacae and sphincter cloacae, together with the penis and its 

 retractor. 



The retractores cloacae are two columns of muscle lying on 

 either side of the mid-line. The bundles arise from the hypapo- 

 physes, and running forward fuse with the fibres of the sphincter 

 ani posteriorly. 



External to these muscles lies a penis on either side with the 

 retractor penis at its posterior extremity, springing from the hypa- 



A sphincter ani surrounds the anus, while on either side of this, 

 external to the penis, is an elongated sphincter cloacae. Lying 

 above the retractor cloacae and penis is a well marked layer of 

 muscle, composed of bundles running from the hypapophyses 

 backwards and outwards to the inferior costo-transverse pro- 

 cesses. These muscles are in series with the sub vertebral rectus 

 described above. 



