PART TENTH. 



TIRO-GENITAL APPARATUS. EMBRY OLOG Y. 



ORIGIN AND DEVELOPMENT OF THE URO-GENITAL 

 APPARATUS. 



THE uro-genital mucous surface and its appendages, on 

 their first appearance, are only a portion of the alimentary 

 canal, of the mucous layer of the 

 blastoderma. At the period when 

 the intestinal canal exists only in 

 the form of a tube, its middle por- 

 tion communicates with the ger- 

 minal vesicle, and each end termi- 

 nates in a cul-de-sac ; on its lower 

 part may be seen a protuberance 

 (B), (Fig. 124), and a partition 

 (E) which separates the primitive 

 tube from- the later protuberance; 

 in this protuberance, which becomes 

 more and more prominent, may be 

 found two cavities: 1. The older 

 1 cavity of the digestive tract or 



rectum; and, 2. In front a uro-geni- 

 tal cavity or sinus uro-genitalis, from which are formed 

 every part of the urinary and genital organs. 



* 1. I, I, Intestinal tube, with the protuberance B, which will soon be sepa- 

 rated bv the partition E. 



2. The partition has extended ; the protuberance B is very much developed, 

 and has given place to the allantols A (the commencement of which, the pedicle, 

 can only be seen), and successively, proceeding from the allantols towards the 

 intestinal tube, the urachus O, the bladder V, the genito-urinary sinus SU, which 

 has also given off three protuberances : for the Wolffian body 1, for the duct 

 of Muller 2, and for the kidney 3. 



