DEPARTMENT OF EMBRYOLOGY. 89 



criteria, based on the morphology of these structures, by which one can 

 recognize sex at an earher period than has heretofore been possible. 

 He finds no evidence of the existence of an indifferent period through 

 which all embryos were supposed to pass before assuming definite male 

 or female characteristics. The younger embryos show constant differ- 

 ences in the form of the phallus and from the earliest differentiation of 

 the genital tubercle they can be divided into two groups. This 

 division is based upon the marked difference in the length of the urethral 

 groove. This seems to be quite constant and without intergradations ; 

 it can be traced backward from the older fetuses, in which the sex 

 can be clearly recognized, to the younger stages, which heretofore 

 have been included in the so-called ''indifferent" period. In one 

 group the urethral groove extends from the base of the phallus 

 nearly to the apex of the glans; these embryos are regarded by Mr. 

 Spaulding as males. Those of the second group, in which the groove 

 is shorter and terminates proximal to the region of the glans, are con- 

 sidered by him to be females. Mr, Spaulding's finished paper is ac- 

 companied by drawings of models and photographs of actual specimens 

 which represent clearly the morphological changes exhibited by the 

 phallus at each stage of its development. These illustrations should 

 prove of great practical value to those who have occasion to determine 

 the sex of embryos at early periods. 



Investigations concerning the morphology of the urinary organs in 

 man have been made by Dr. F. P. Johnson and Dr. M. B. Wesson, of 

 the Brady Urological Institute. The former has studied the develop- 

 ment of the urethra and its associated glands, the latter has investi- 

 gated the embryology of the sphincter muscles at the neck and base 

 of the bladder. The determination of the finer anatomy of these 

 structures has proved to be a matter of considerable clinical im- 

 portance, and these investigators, by carefully working out the archi- 

 tecture of the early and simpler stages, have provided the necessary 

 groundwork for the understanding of the anatomy in the adult. 



Dr. Johnson's study begins with embryos of 55 mm. crown-rump 

 length and follows the development of the urethra to term. Models 

 were made from serial sections of selected stages. By comparing the 

 models with the serial sections, it was possible to determine the 

 number and distribution of the small urethral glands and the formation 

 and consistency of the mucosal folds. Observations were also made on 

 the development of the prostatic glands and Cowper's glands, and upon 

 the formation of the prepuce. In the cleavage of its epithelium, the 

 latter presents an interesting problem which still remains to be solved. 



It is shown by Dr. Wesson's study that there does not exist at the 

 vesicle orifice a simple sphincter muscle, as had been generally sup- 

 posed. Instead, we are dealing with loops of muscular fibers which 

 arise from and are closely connected with the longitudinal and circular 



