253 BOTANICAL GAZETTE [apeil 



Just to what extent precipitation during incubation is a factor in 

 inhibition is difficult to say. The results show that precipitation 

 occurs in concentrations which cause total and often only partial 

 inhibition. However, with zinc (Tables IX and XII) and silver 

 (Tables XIV and XV) we find total inhibition without precipitation. 



The enzyme itself, that is, the substance exhibiting zymolytic power, 

 is probably a reversible colloid, and since it was not precipitated by the 

 neutral salts used, it may be assumed to have gone into colloidal solu- 

 tion rather than into suspension. Perhaps it also is a hydrolyte hber- 

 ating both H and OH ions. If this is the case, its saponifying power 

 may be associated with its hydrolytic dissociation, just as has been 

 that of the salt hydrolytes. The toxicity of the salt might even be 

 referred to the possibility that the excess of H or of OH ions resulting 

 from the hydrolysis of the salt prevented the hydrolytic dissociation of 

 the enzyme substance and therefore caused the inhibition'*' (p. 214). 

 If so, to what is the toxicity of the neutral salts to be referred ? Also, 

 why are the very highly diluted and therefore neutral solutions of silver 

 and mercury capable of causing total inhibition ? May not the chemi- 

 cal nature of the atom be a factor ? Since convincing evidence is not 

 available for a negative answer, and since theoretical argument based 

 upon the negative assumption leads to embarrassing conclusions,'^ it 

 is obvious that in any effort to discover final causes this possibility 

 should not be ignored. 



The tests with equicationic solutions show the futility of any attempt 

 at generalization in that direction and at every hand exceptions seem 

 to arise. 



CONCLUSION 



In the zymolytic saponification of ethyl acetate as in that of ethyl 

 butyrate, the toxicity of the salts tested does not under the conditions 

 specified vary inversely with the decomposition tension of those salts. 



The concentration of the enzyme is a factor in relative toxicity in 

 some cases. 



i^Bredig, G., Beitrage zur Stoichiometric der lonenbeweglichkeit. Zeitsch. 

 physikalische Chem. 13:191-288. 1894. 



17 Berg, /. c. pp. 15-20. 



Note. — In referring to Pond (/. c), note the following errata: p. 274, bottom line, 

 "Zinc and cadmium" should read Zinc and barium; p. 283, line 13 from top, "Table 

 XIII" should read Table XIV. 



