ON EMBRYONIC DIFFERENTIATION 



273 



In this connection, it may be held as a rule that the 

 quantity of each alvine evacuation is determined by the 

 quantity containable, consistently with the absence of 

 local discomfort, within the post-sigmoid portion of the 



FIG. no. VERTICAL SECTION OF THE PELVIS AND ITS VISCERA IN THE 

 MALE. ^ (Allen Thomson, after Houston.) 



This figure is introduced to illustrate the form, position, and relations of the rectum ; 

 it also shows the bladder and urethra with the pelvic inflection of the peritoneum 

 over these viscera : r, r, r, the upper and middle parts of the rectum, and at the 

 middle letter the fold separating the two ; r, a, the lower or anal portion ; v, the 

 upper part of the urinary bladder ; v' , the base, at the place where it rests more 

 immediately on the rectum ; /, the prostate gland and prostatic portion of the 

 urethra ; b, the bulb ; c, c, the corpus cavernosum penis and suspensory ligament ; 

 sc, the scrotum ; s, symphysis pubis. 



rectum, and that the consistency of its substance, or 

 material, and the responsiveness of the combined machinery 

 of evacuation, determine the manner, and method, of its 

 ultimate elimination, or excretionary disposal. 



In connection with the assignment of sphincteroid 

 powers, to the anatomical mechanism of the sigmoid 



