() AUGUSTUS G. POHLMAN 



bit) , a fold of mesoderm appears at the cephalic extremity of each 

 lateral cloacal wall, and extends little by little toward the caudal 

 end of the cloaca. These lateral folds encroach upon the lumen 

 of the cloaca and divide it into two canals, the one dorsal or 

 rectal, and the other ventral or vesico-urogenital." 



That these opinions, while they are in the main contrary to the 

 views of Keibel although they appeared at an earlier date, are 

 accepted at the present time can be illustrated by an extract from 

 Zuckerakndls Handbuch der Urologie ('03): '' In the second 

 fetal month, the proximal segment of the allantois widens to form 

 the bladder, while the distal and narrow portion (urachus) ob- 

 literates to form the Lig. vesico-umbilicale,'' "The division of the 

 cloaca is accomplished by three folds, a median and two lateral. 

 The former occupies the angle between the allantois and hind 

 gut, while the latter are developed in the lateral walls of the cloaca." 



The investigations of Tourneux ('94) agree with those of Keibel 

 in that he also states the cloaca to be a closed sac. His objec- 

 tions to the method of cloacal division as described byRetterer 

 are as follows: ''The form of the inferior border of the recto- 

 urogenital septum is that of a vaulted arch and not that of an 

 elliptical arch with thevertex upward — afact easity demonstrated 

 in frontal sections. In addition to this, the transverse sections 

 show that the lateral folds are found only toward the summit of the 

 arch and converge rapidly. Further, the septum shows no signs 

 of an epithelial raphe at the supposed line of fusion to indicate 

 the transition that one encounters, as Keibel states, at the line 

 of union of the palatine ridges." 



Nagel ('96) answers Keibel's article by stating ''If Keibel did 

 not find the facts as presented by myself in all of his embryos of 

 11.0 mm. and upwards, then the embryos are at fault." "Fur- 

 thermore in order that an embryo may be declared of scientific 

 value, I demand that the urogenital canal be open into the cloacal 

 pit in all embryos over 8.0 mm., and that the cloacal membrane 

 have disappeared as far as the tip of the genital eminence. Inas- 

 much as th& allantois contained within the umbilical cord is prac- 

 tically obliterated at this stage, where could the secretion from the 

 mesonephros be stored up if the cloacal membrane were intact?" 



