$6 GLANDS IN HEALTH AND DISEASE 



almost infinitesimal in amount, and to devise not 

 only qualitative, but quantitative methods for de- 

 tecting such amounts, appears to be a problem 

 beset with endless difficulties. Yet what seems to 

 approach the impossible has been accomplished. 

 In this connection it is of interest to note that 

 physiological methods, like spectroscopic methods 

 in many cases, and the electroscopic method in the 

 case of radium, have proved themselves more deli- 

 cate than chemical ones. For example, Meltzer 

 has devised a physiological procedure which de- 

 pends upon the action of adrenaline in dilating the 

 pupil of the enucleated eye of a frog; and claims 

 that a strength of hormone one part in 20 million 

 can be detected. Using a loop of intestine and re- 

 cording how its movements are inhibited by adrena- 

 line, is said to be so delicate as to detect one part 

 of hormone in 400 million. 



The best chemical method so far devised is one 

 based on colorimetric comparisons, due to Professor 

 Folin, of Harvard. It depends on the blue color 

 obtained when adrenaline is added to phosphotung- 

 stic acid. This blue color can be noticed in dilu- 

 tions of adrenaline of one part to three million. 



Adrenaline and sugar metabolism. The relation 

 of adrenaline to sugar metabolism will be referred 

 to in Chapter VII. Here it should be said that the 

 injection of this substance into the body of an ani- 

 mal increases the quantity of sugar normally found 



