196 JOHN LEWIS BREMER 



vessels of the Wolffian body can be traced toward the renal 

 blastema. At no time does the kidney seem to be without 

 arterial blood, from one source or another. The persistence 

 of any of these mesonephric connections would make possible, 

 as explained above, the presence of a spermatic branch of the 

 renal artery; but an anomaly from this source must necessarily 

 be extremely rare in animals with large Wolffian body, because 

 it would depend upon the blocking of the more direct channels. 



In man there is neither an excessive curvature of the body 

 nor a large Wolffian body, so that theoretically the renal artery 

 could be derived from the mesonephric, lateral, or dorsal seg- 

 mental roots of the -plexus; yet normally it is not directly derived 

 from any of these. The reason for this is found in the precocious 

 development of the suprarenal gland in man. 



Goormaghtigh (17) finds the first growth of the mesothelial 

 cords which form the cortex of the suprarenal gland at about 

 ten days in the white mouse, about twenty days in the guinea- 

 pig, but states that these cords do not separate from the meso- 

 thelium to form a recognizable organ until much later. Sub- 

 stituting the white rat for the white mouse, of which no specimens 

 were available, I find that the gland is first seen as a large organ 

 at about 14 days, 8.0 mm. ; in the guinea-pig it occurs in embryos 

 of about the same length. In the cat the suprarenal cortex 

 can be recognized as such at about 11.0 mm., in the pig at 15.0 

 and at corresponding ages in the rabbit and sheep. In all of 

 these animals, the organ occupies at this time the upper abdomi- 

 nal region, so that there is a long distance, representing five or 

 six segments, between the upper pole of the kidney and the 

 lower limit of the suprarenal gland. 



The suprarenal arteries are also derived from the perioartic 

 plexus or, if this has partially broken down, from its aortic roots. 

 Thus in a cat embryo of 1.5.6 mm. (H.E.C. No. 1983) an upper 

 suprarenal artery springs from a loop between a dorsal segmental 

 vessel and the coeliac axis. The mechanical forces which influ- 

 ence the choice between the aortic roots are similar to those 

 explained for the renal artery, but may difi"er in the upper and 

 lower levels of an organ which becomes as long as does the supra- 



