264 INTERNAL SECRETION 



An abnormal activity on the part of the adrenal system 

 would, in my opinion, not only produce a heightened vascular 

 tone, but would also manifest itself in other signs of irritation on 

 the part of the sympathetic nervous system. A manifestation of 

 such a condition, in the form of a well-defined clinical entity, is, 

 however, at present unknown. As far as we Can judge, Graves's 

 disease is invariably associated with an increase in the adrenalin 

 contents of the blood, which is proved both by the mydriatic 

 property of the serum and by the tonic action of preparations of 

 the uterus. Fraenkel found that the adrenalin contents of the 

 blood in Graves's disease were increased to from four to eight 

 times the normal, the total amount in these patients being 50 to 

 100 mg., as against the 12^ mg. present in the blood of normal per- 

 sons. It is remarkable in this connection that an increased blood- 

 pressure is not, as a rule, associated with Graves's disease. 



THE FUNCTION OF THE ADRENAL SYSTEM. 



From the facts which have been presented in the foregoing 

 pages, the nature and functions of the adrenal system may be 

 defined as follows : 



The adrenal system is an essential portion of the body of all 

 vertebrate and some invertebrate animals. It has a specific struc- 

 ture, characterized morphologically and genetically by peculiar 

 features ; the nature of its function is distinctive and is probably 

 dependent upon origin. 



The structure of the adrenal system is characterized by the 

 peculiar nature of the elements of which it is built up, namely, the 

 chromaffine cells. 



The adrenal system is distinguished anatomically by its wide 

 distribution over the whole of the body, as well as by the lack 

 of independence of its parts. These conditions are explained by 

 the history of the development of the system. 



The chromaffine cells are derived from the same primordial 

 beginning as the sympathetic ganglia and they develop, up to a 

 certain point, as part of the sympathetic nervous system. A con- 

 siderable portion of the adrenal system permanently retains its 

 genetic relationship with the sympathetic, becoming associated 

 only in part w 7 ith the blood-vessels. The so-called free portions 

 of the system are, however, found distributed all over the body in 

 connection with the sympathetic nerves and ganglia. They 

 occur partly in the form of more or less extensive agglomera- 

 tions of chrome-brown cells, called paraganglia (Kohn) ; and 

 partly as isolated structures attached to the great vessels such 

 as the suprarenal bodies of the Selachians, the carotid gland, and 

 the accessory organs of the sympathetic (Zuckerkandl) though 

 the relationship of these bodies to the adrenal system has been 

 recognized only in comparatively recent times. The lack of in- 



