328 



EMBRYOLOGY. 



they are composed become longer and more tortuous ; they 



evidently secrete, and with their elongated common ducts, to 



which they look as if they 

 were attached, terminate in 

 the cloaca ; betwixt their 

 component shut sacs num- 

 bers of small points, which 

 consist of little convoluted 

 hanks of vessels, in every 

 particular like the Malpi- 

 ghian bodies of the kidney, 

 may be observed. The kid- 

 neys show themselves be- 

 hind and above the Wolffi- 

 an bodies on either side of 

 the spinal column ; at first 

 they are lobulated greyish 

 masses, which sprout by 

 the outer edges of the 

 Fig. 352. Chick with part of the Wolffian bodies; this is 



yolk, a, a, which communicates, hy plainly to be seen on the 



means of the delicate vitello-intestinal 



duct, with the noose of the jejunum b, 



which at this time lies within the 



funis umbilicalis ; c, c, vasa lutea. B, 



separate views of the anterior extremity, 



which shows a distinct division into 



three digits, o, and of the posterior ex- 

 tremity, vvhich shows traces of four 



digits, b 



sixth day, perhaps even 

 sooner ; the ureters are 

 formed afterwards as their 

 especial excretory ducts. 

 The kidneys arise as inde- 

 pendent formations ; and, 

 independently of them, the 

 capsulee supra-renales are 

 evolved on their upper or anterior edge. The reproductive 

 organs, which had appeared as little marginal lappets, now 

 form two longish-shaped white bodies, and lie behind the 

 supra-renal capsules, at some little distance from these, on the 

 inner edge of the Wolffian body ; they are still of like size, 

 and it is impossible to distinguish whether testicles or ovaria 

 will be produced; so that of all the principal organs the ge- 

 nital are those that are the latest recognizable in their rudi- 

 ments, and distinguishable in their future special forms. 

 The vessels of the allantois are developed with great vigour ; 

 two arteries arise from the aorta, and a large vein runs on 

 the under edge of the liver to the vena cava, along with the 



