DEVELOPMENT OF THE RECTUM O 



the rectum bj- Testut, Kopsch-Rauber, and Spalteholz. The 

 terms 'pars pelvina' and 'pars perinealis' are employed for the 

 two parts of the rectum by Waldeyer in Joessel's Lehrbuch. 

 Poirier et Charpy use the terms 'rectum pelvien' and 'rectum 

 perineal.' Morris and Gray apply no especial name to the first 

 part. The former calls the second part the 'anal canal,' the 

 latter the 'inferior' or 'prostatic' portion. Gray, like Spalteholz, 

 Kopsch-Rauber, and others, regards only the lower widened 

 portion of the first part as the ampulla recti. Corning considers 

 as synonyms for the first part of the rectum the terms pars ampul- 

 laris recti, pars pelvina, and flexura sacralis, while for the second 

 part, pars analis recti, pars perinealis, and flexura perinealis ; and 

 says that the three sets of terms are applicable from the stand- 

 points of physiology, topographic anatomy, and descriptive anat- 

 omy, respectively. 



Likewise in the case of boundary lines between the pars analis 

 recti and the ampulla recti one finds varying descriptions. Thus, 

 the tip of the coccyx, the pelvic diaphragm, and the beginning of 

 the pelvic floor are all given. It has also been described merely 

 as the beginning of the narrower portion found below the widened 

 ampulla. Still another line of division is given as the ano-rectal 

 line, the point at which the simple columnar epithelium leaves 

 off and a stratified columnar epithelium begins. However, these 

 points do not exactly coincide. The ano-rectal line, even in late 

 fetal stages, does not correspond to the beginning of the narrow 

 portion of the rectum ; while the statement that it ends at the tip 

 of the coccyx is indefinite. 



The terms as found in the B.N. A. list are used consistently 

 throughout this paper whenever possible. As regards the mean- 

 ing of the term 'ampulla recti,' the work of Merkel and Corning 

 is followed, designating the whole of the first portion of the rectum. 

 By 'pars analis recti' will be meant that portion which has, under 

 ordinary conditions a much narrower caliber than the ampulla. 

 This portion which develops from a definite embryonic struc- 

 ture, does not have as its upper limit the histological ano-rectal 

 line. Its upper boundary corresponds fairly closely, however, 

 with the beginning of the pelvic floor. 



