266 INTERNAL SECRETION 



internal secretory organs. The morphology of the secretory pro- 

 cess is well known. The product of secretion is formed in the 

 granules in the cells and is transferred to the blood-stream in fluid 

 form. Not only have we morphological proof of the secretion, but 

 its presence in the venous blood has been demonstrated chemically ; 

 in the face of these facts, it is not possible to doubt the 

 secretory function of the adrenal tissue. The objections which 

 Kohn advanced upon morphological and genetic grounds against 

 the inclusion of the adrenal system among the internal secretory 

 organs, is, however, justified to this extent ; the chromaffine cells 

 do not conform to the type of the epithelial cells ; and agglomera- 

 tions of chromaffine cells do not conform to the type of the true 

 glands. But from the physiological standpoint, the specific pro- 

 ductive activity of the adrenal tissue fully justified its inclusion 

 among the internal secretory organs. 



There is a continuous formation by the adrenal system of a 

 substance of known chemical constitution, named adrenalin, which 

 may also be obtained synthetically. This substance passes into 

 the circulation and is carried by the blood-stream into all the 

 tissues of the body. The passage of adrenalin by way of the 

 nerves, which Lichtwitz assumed, has no physiological signifi- 

 cance. 



Adrenalin is a typical dissimilatory hormone, which acts 

 upon certain tissue elements and reinforces their katabolic activity. 

 The activity of this hormone is exclusively confined to organs with 

 a sympathetic innervation, and it invariably coincides with the 

 results produced by electric stimulation of the sympathetic nerves 

 supplying those organs. Adrenalin produces its effect, not upon 

 the specific functional portion of the reacting cell nor upon the 

 nerve-ending itself, but upon a portion of the cell body situated 

 in the neighbourhood of the nerve-ending, the so-called receptive 

 substance which, in the involuntary muscles, is termed the myo- 

 neural junction. The activity of the hormone elaborated by the 

 adrenal system, is the permanent expression, during the life of the 

 individual, of the genetic relationship between the adrenal and the 

 sympathetic nervous systems. 



It must not be imagined that adrenalin is merely a sympathetic 

 stimulant and therefore of use only in promoting the functions of 

 the organism ; on the contrary, its activity is fundamentally and un- 

 ceasingly necessary to the normal function of the entire sym- 

 pathetic system. The parallel between the developmental pro- 

 cesses and the dependence, shown in many directions, of the 

 activity of the sympathetic upon the presence of adrenalin, as 

 well as the continuous formation of this hormone expressed by 

 its presence as a physiological constituent of the blood point to 

 the fact that adrenalin is essential to the maintenance of sym- 

 pathetic tone and to the normal function of the sympathetic system. 

 These factors show, moreover, that changes in the condition of 



