302 INTERNAL SECRETION 



This assumption of a function on the part of the interrenal 

 tissue by which the raw material of adrenalin is provided, would 

 explain the importance of the interrenal tissue to the life of the 

 organism ; and would account for those instances where animals 

 survive double epinephrectomy, by the presence of accessory inter- 

 renals which thereafter become hypertrophied. In such cases as 

 these, Poll believes that the organism returns, to a certain extent, 

 to a previous developmental stage, that at which the two supra- 

 renal systems are topographically independent, as in fish. 



Fascinating though this hypothesis of an interdependent 

 function on the part of the two suprarenal systems may be, it 

 must be remembered that its sole foundation at present is upon 

 morphological grounds ; that it rests entirely upon the ontogenetic 

 and phylogenetic association of portions of the interrenal and 

 adrenal systems, together with the peculiar conditions which 

 govern the vascular communication between the two systems. It 

 must not be forgotten that, up to now, all attempts to prove a 

 homogeneity of function on the part of the suprarenals, whether 

 by experimental biology or from the results of human pathology, 

 have signally failed. 



It must be frankly confessed that, as things are at present, we 

 have as little certain knowledge concerning the functions of the 

 homogeneous suprarenal as we have of the function of the inter- 

 renal tissue; and it is only by means of investigation of the latter 

 that we can hope to arrive at any definite information concerning 

 the former. 



CAROTID GLAND AND COCCYGEAL BODIES. 



The carotid gland, w r hich we have learnt to regard as a por- 

 tion of the adrenal system, may be briefly described as follows. 

 In man, this organ measures 5 to 7 mm. in length, 2^ to 4 mm. 

 in breadth, and ij mm. in thickness. It is situated at or within 

 the bifurcation of the common carotid artery and, on account of 

 its situation and its considerable nervous provision, was, by the 

 older anatomists, called the intercarotid ganglion. 



Luschka (1862) was the first to undertake an exact micro- 

 scopic examination of this body ; his findings led him to the 

 conclusion that it was a glandular organ auxiliary to the cervical 

 sympathetic. He believed it to be a nerve gland, and named it 

 glandula carotica. Arnold (1865) next declared that the glandular 

 structure described by Luschka was, in reality, an arrangement 

 of blood-vessels, the walls of these vessels being formed of several 

 layers of epithelium ; he recommended that the organ should be 

 called glomeruli arteriosi intercarotici. According to Eberth (1870), 

 however, the cell-agglomerations resembling epithelium by which 

 the vessels are surrounded, do not form a true epithelium, but a 

 vascular perithelium. Waldeyer (1872) compared the epithelial 



