12 ANATOMY 



COMPARATIVE ANATOMY 



Tissues corresponding to the interrenal body or the cortex 

 of the mammalian adrenal have not been demonstrated ana- 

 tomically in animals below the cyclostomata (hags and lam- 

 preys). The homologue of the chromaphil or medullary tissue 

 has, however, been demonstrated in a number of the lower 

 invertebrates. The ease with which this chromaphil tissue 

 may be identified (staining reactions, pressor effects, etc.) have 

 aided in its detection in these lower forms. It is possible that 

 the discovery of a corresponding micro-chemical or biological 

 test for the internal secretion of the interrenal tissue may also 

 lead to the demonstration of the interrenal homologue in the 

 lower genera. 



Poll and Sommer 509 have described cells in the abdominal 

 ganglia of leeches (Hirudo medicinalis, Gnathobdella, and 

 Rhynchobdella) which resemble the chromaphil tissue of the 

 higher genera. That these cells probably secrete epinephrine 

 was demonstrated by Biedl 56 and by Gaskell 211 who showed 

 that extracts of the ganglia of the leech inhibit the contractions 

 of the uterus of the virgin cat, a reaction typical of epinephrine. 

 In the mollusc {Paludina vivipara), Leydig 396 described tissues 

 which he thought corresponded to the chromaphil tissue of 

 vertebrates. Vincent, 646 however, failed to obtain a pressor 

 effect by injecting extracts of this tissue and hence Ley dig's 

 opinion is open to question. On the other hand, Roaf, 

 Nierenstein, and Poll 649 have described tissues in Purpura 

 lapillus, and in Nephthys scolopendroides which resemble closely 

 the chromaphil tissue of the adrenal. 



In none of the above species has any evidence been adduced 

 to indicate the existence of any interrenal tissue. The lowest 

 vertebrates in which both adrenal elements have been shown 

 to exist are the cyclostomata. In the lamprey (Petromyzon) 

 Giacomini 216 described small lobulated structures projecting 

 into the lumen of the posterior cardinal veins and renal arteries 



