this case the chemical messenger is a product of activity which is 

 common to all protoplasm and must be excreted by the cell as a condi- 

 tion of its further activity. The adaptation in this case therefore is 

 not the formation of a special substance which shall exert a specific 

 influence on some distant organ, but the development in this distant 

 organ of a specific sensibility to the common product of excretion of the 

 first organ. We may, perhaps, assume that the more specialised mes- 

 sengers, which we shall have to consider in detail later, were at first 

 accidental by-products of the selfish activity of the organ producing them, 

 the first step in the development of a correlation being the acquisition of 

 a sensibility to the substance in question by some distant organ. 



The only other example of such a reaction, in which we know both 

 the source and nature of the chemical messenger and the exact nature of 

 the effects which it produces, is the suprarenal gland. Since the time of 

 Addison we have known that atrophy of these glands in man leads to a 

 disease characterised by the three cardinal symptoms of bronzing, vomit- 

 ing, and extreme muscular weakness. Most of the attempts to reproduce 

 this disease in animals have failed, owing to the fact that death follows 

 the excision of both glands within 24 hours ; the extreme muscular weak- 

 ness is certainly produced, and this is attended by a profound fall in the 

 general blood pressure. In 1894 Oliver and Schafer showed that from 

 the medulla of the suprarenals a substance could be extracted which, on 

 injection into the circulation, caused marked rise of blood pressure and 

 increased strength of the heart beat. Since the publication of these 

 observations our knowledge concerning the nature and actions of this 

 substance has progressed rapidly. The researches of Jowett in this 

 country, and of von Furth in Germany, have shown that the active 

 substance is a definite chemical compound derived from pyrocatechin 

 and having the formula 



OH/ \.CH(OH).CH r NIICH 3 , 



Takamine, by the elaboration of a method for its preparation from 

 the gland in a state of purity, has placed in the hands of the druggist a 

 means of supplying the substance in bulk to the medical profession for 

 therapeutic purposes. The exact knowledge of the constitution of 

 adrenalin thus acquired has paved the way for the actual synthetic 

 formation of this substance. Here, again, there has been a keen inter- 

 national rivalry, and the credit of its synthesis must be divided between 

 this country and Germany. It is gratifying that the only original investi- 

 gation of the subject which has yet been published as a contribution to 

 science is the admirable account by Dakin of his synthesis, not only of 

 adrenalin but of a whole array of substances, which are closely allied to 

 this body in their chemical structure as well as in their physiological 

 influence on the animal organism. 



