COPPER, ENZYMES, AND FERTILIZATION. 91 



nia, whereupon the xanthate gave a very faint though unmistakably- 

 positive test. 



E. Pepsin (Parke-Davis). 



Also positive ; faint after precipitation of copper by iron hydroxide. 



These tests prove that copper occurs in preparations of pancre- 

 atic enzymes and pepsin. The association with lipolysin, there- 

 fore, is not a necessarily isolated instance, but very possibly a 

 special illustration of a general rule. Indeed, the studies of von 

 Euler and Svanberg ('20 2 ) definitely foreshadow a natural relation 

 between enzymes and heavy metals. 



IX. Localization of Copper in Eggs Exposed to Copper 



Solutions. 



Normal eggs, in addition to secreting copper compounds, remove 

 copper sulphate from sea-water when this salt is present. In eggs 

 so exposed we should expect differences, if not in distribution, 

 then at least in the concentration of the copper which they contain. 

 Such analyses seem doubly worth while, for they seem not only to 

 control and correct the observations on normal material, but may 

 ultimately throw some light on the machinery of copper fixation 

 and metabolism in general. 



Tests consequently were made on material with a total volume 

 of .5 c.c. exposed for 20 minutes to 5 c.c. of a 1/180 n Cu solution 

 in sea-water. In every other respect the eggs were treated as 

 described in section VII. Moreover, the material was from the 

 same lot as that used for the localization of copper in normal eggs. 



1. Copper Absorbed by the Chorion. 

 From the experiments of section IV. we expect for the jelly of 

 exposed eggs a copper content greater than that found in the nor- 

 mal chorion. This expectation, of course, is realized, as can be 

 shown by means of the hematoxylin test with entire eggs. Super- 

 ficially such eggs take on an unmistakable blue color which micro- 

 scopic examination localizes distinctly in the jelly. The same 

 effect is gotten with the triple-nitrite test, only the color is then 

 black instead of blue. 



