CHEMOTROPISM 141 



to a liquid containing 0.001 per cent, of peptone or of 

 meat extract. It is stated that cholera bacilli are strongly- 

 attracted by potato sap. Pfeffer found also that the sper- 

 matozoa of certain mosses are positively chemotropic to 

 cane sugar solution in dilutions of 0.1 per cent. 



Pfeffer 's work preceded the discovery of electrolytic 

 dissociation, and his pupils Buller 89 and Shibata 465 

 made some of the additions required by the theory, namely, 

 that it is the malate anion which acts in the case of the 

 spermatozoa of the ferns, and that when the anion is 

 offered in the form of malic acid the H ion counteracts 

 the effect of the malate anion. 



Shibata made extensive experiments on the chemotrop- 

 ism of the spermatozoa of Isoetes 465 which he found posi- 

 tively chemotropic for the malate anion, and also for the 

 succinate, tartrate, and fumarate anion, when offered in 

 the form of their neutral salts. The anion of the stereo- 

 isomere of fumaric acid, namely of maleic acid, was with- 

 out effect. This indicates a high degree of specificity of 

 these reactions. Neutral sodium malate acted best in 

 dilutions from m/100 to m/1000, but some action could 

 still be discovered in m/20,000 solutions. 



When malic acid was used no positive chemotropism 

 could be discovered in solutions of m/100 or above on 

 account of the contrary effect of the hydrogen ion, and 

 the spermatozoa of Isoetes did not even go into capillary 

 tubes containing m/1000 malic acid. When any acid 

 other than malic was added to sodium malate the motion 

 of the spermatozoa into the tube was prevented, even 

 a m/6000 HC1 solution still had such an effect. 



Shibata studied especially the mode by which the 

 spermatozoa are oriented chemotropically by malates and 

 found that the reaction consists always in a turning of 



