510 



Prof. S. Vincent. 



[Apr; 6, 



the operation quite as fast as its fellows which had not been touched. The 

 animal was killed when five months old, and no discoloration of the skin or 

 hair could be detected. Commenting upon this Prof. Schiifer says " the rat 

 happens to be the one common animal which is able to withstand complete 

 removal of both suprarenal capsules. The reason for this was not at the 

 time apparent, although it is now known, for the rat is exceptional in 

 possessing in various parts of the back of the abdomen and pelvis numerous- 

 small glandular structures which are composed of cells having the 

 characteristic features and functions of the cells of the suprarenal 

 medulla." 



I have carefully examined several white rats, but have failed to find any 

 traces of extra-adrenal chromaphil tissue. There is probably, however, some 

 difference in this respect between the different varieties of rats, for Dr. Kohn 

 informs me that he has found an abdominal chromaphil (paraganglion 

 aorticum abdominale) in a rat which he dissected, and he has sent me an 

 illustrative sketch. But he is of opinion that the rat does not possess a 

 greater abundance of chromaphil tissue than other animals. 



From the large size of the chromaphil body in the dog one would expect 

 to find this animal more resistant to adrenal extirpation than other animals, 

 if the chromaphil tissue be looked upon as essential to life. But the 

 experimental evidence bearing upon the relative importance to life of cortex 

 and medulla is very contradictory.* 



b. Microscopic. 



My investigations upon the minute structure of tlie abdominal chromaphil 

 bodies liave been confined to the dog. In this animal the body is large 

 enough to be found without treatment with bichromate, and so can be dissected 

 out and fixed in any fluid one chooses. 



In proitarations made with bichromate solutions {e.g., Koliu's fluid, vide 

 supra) the cluomaphil cells are stained of a tint which varies from a light 

 yellow to a deep brown, according to the duration of the treatment with the 

 solution, and apparently also according to pliysiological conditions in tlie 

 cells. 



I'late 18, lig. 4, sliows a transverse ■ section through the ab(U)niinal 

 chromaphil l)()dy (ilog) fixed in Kohn's fluid. The section is seen to be 

 divided u]i into ii nuinl)er of irregular areas which represent the cross-sections 

 of cohuniiH of cells which run longitudinally. The width of these columns 

 varies considerably (see Plate 13, iigs. 1 and 4). They are divided 



* l''()r a (liwuHHion of IIiIh Hiihjcct Vincent, ' KpgcLiiiwo dcr T'lij'niol.,' 1910. 



