PARALYSERS 357 



enzymes may be mentioned inorganic substances such as 

 mercuric chloride or cyanide, arsenious oxide, sulphuretted 

 hydrogen, ozone, and organic compounds such as chloro- 

 form, chloral, formaldehyde, hydrocyanic acid, phenylhydrazine 

 aniline, alcohol, etc. ; the influence of these substances on 

 different enzymes varies considerably ; thus, for example, 

 alcohol usually acts as a paralyser, but on lipase it has a 

 stimulating effect. 



The majority of the substances included in the above list 

 also act as poisons to colloidal solutions of metals ; the 

 peculiar phenomenon of the recovery of metallic colloidal 

 solutions from poisoning by hydrocyanic acid, is also met 

 with in the case of the enzymes, and is likewise attributed to 

 the oxidation of the poison. 



The mechanism of toxic action is as yet unexplained ; it 

 is assumed that some form of chemical combination between 

 the paralyser and the substrate enzyme or activator takes 

 place.* 



The work of Caldwell f on the effect of toxic agents upon 

 bromelin, the proteolytic enzyme of the pineapple fruit, may 

 be cited in illustration. The prepared enzyme (see p. 370) 

 was dissolved in water so that each cubic centimeter contained 

 006 gram and the solution was rendered acid or alkaline by 

 the addition of hydrochloric acid or sodium hydrate of a con- 

 centration of M/32. Five c.c. of the enzyme solution was 

 placed in a series of test tubes together with I gram of boiled 

 granulated egg albumen ; then to each tube was added a solu- 

 tion of the paralyser. 



The tubes were then placed in a water bath and kept at a 

 temperature of 40 C. for twenty-four hours. At the end of 

 this period, the liquids were filtered, if necessary, to remove 

 any albumen, and tested for peptones, leucine and tyrosine by 

 the biuret and tryptophane reactions, confirmatory tests being 

 applied if necessary. 



In the following table the metals are arranged in their 

 order of toxicity, the top ones being the most poisonous, 

 and are compared with the results obtained by Matthews J 



*Cf. Loewenhart and Kastle: " Amer. Journ. Chem.," 1903, 29, 397, 563. 



t Caldwell : " Bot. Gaz.," 1905, 39, 409. 



J Matthews: "Ann. Journ. Physiol.," 1904, 10, 290; 1904, n, 455. 



