THE HUMAN PROSTATE GLAND 303 



formed by these bands of muscle the fibers appear to interlace 

 indiscriminately. 



Delbet 14 declares the trigonum vesicae to be an appendage of 

 the urethral walls. Congenital absence of a ureter shows the 

 trigonum to be lacking on that side. Passavant has described a 

 case in which the trigone was entirely separate from the bladder 

 wall. 



In regard to the internal sphincter of the human bladder Ver- 

 sari 15 concludes from his investigations that (1) The smooth muscle 

 sphincter of the urinary bladder of man constitutes a structure 

 by itself, which develops independently of the middle (circular) 

 layer of the bladder, the circular muscle layer of the urethra and 

 the musculature of the ureters. (2) The sphincter is made up of an 

 urethral and a trigonal portion, and it is the urethral portion only 

 which assumes the form of a ring surrounding the initial part of the 

 urethra. The first groups of the fibers of the sphincter arranged 

 in bundles correspond to the anterior arch of the urethral por- 

 tion; from there immediately follow those of the urethral portion 

 of the posterior arch, and these last are apparently those of the 

 trigonal portion. The posterior arch of muscle extends little by 

 little, with new bundles either upwards to occupy part of the tri- 

 gonal area or downwards along the posterior wall of the urethra, 

 so that it comes to have an extent much greater than the anterior. 

 On the other hand, the older view held by Krause, Hyrtl, Gegen- 

 bauer and others is that the sphincter is a continuation downward 

 of the circular musculature of the bladder. 



The seminal vesicles begin to develop at about the third month 

 (McMurrich). 16 Pallin found that the ejaculatory ducts show no 

 suggestion of smooth muscle at the sixth month. The colliculus 

 seminalis of man is, according to D. Berry Hart, 17 the analogue of 

 the hymen and lower one-third of the vagina, the Mullerian ducts 

 not being represented in the adult human male except by the hyda- 



14 Poirier and Charpy: Traite d'anatomie humaine, vol. 5, p. 110. 



15 Versari, Ric. d. Lab. d. Roma, vol. 13, 1907. 



lfi McMurrich, The development of the human body, Philadelphia, 1902. 

 17 Hart, A contribution to the morphology of the human urino-genital tract, 

 Jour, of Anatomy and Physiology, 1901, p. 330. 



