The Unity of the Organism 



the proposal is worth quoting. "I propose therefore pro- 

 visionally to apply the word thyrine to denote the active 

 principle, whether it be identical with or contained in the 

 iodothyrin of Baumann or not." 8 



Thyrine then becomes the name of a substance the source 

 and some of the activities of which are known, but whose 

 main physical and chemical attributes are unknown. 



Concerning the mode of action of thyrine there are sev- 

 eral divergent views, all based on some evidence and so 

 perhaps not entirely antagonistic. Is the antitoxic theory 

 of Luciani 9 partly right, right as regards the parathyroid 

 secretion (Moussu, Vassale and Generali), and partly 

 wrong, wrong as to the secretion of the thyroid proper, this 

 being trophic rather than antitoxic? 10 May there not be 

 more in the enzymic theory suggested some years ago, than 

 later writings have been inclined to favor? Does the fact 

 that internal secretions seem to be simpler than enzymes, 

 as indicated by their greater resistance to heat, preclude the 

 possibility that their normal mode of action is of the enzyme 

 type after all? That is, may it not be necessary to extend 

 the conception of enzymic action (which is surely generic 

 anyway) to include the various sorts of activity presented 

 by hormones, understood in the sense given it by its origi- 

 nators ? 



But neither can the resemblance of internal secretions 

 to drugs, so far as their action is concerned, be overlooked. 

 This has been dwelt upon by Schafer " and has important 

 bearings on the problems of the origin as well as on the 

 chemical nature of the substances. 



Another aspect of the mode of action of internal secre- 

 tions is that of whether the effects are to stimulate or inhibit 

 the activity of the organ or tissue on which they operate. 

 Schafer and others make a special point of this, directing 

 the attention to the fact, by'way of illustration, that the 

 adrenaline of the suprarenal medulla causes contraction of 



