36 CHEMICAL AGENTS AND PROTOPLASM [Ch. I 



Inorganic Salts. — Pfeffee* ('88, p. 601) tried various salts 

 of potassium; viz. chloride, phosphates, nitrate, sulphate, car- 

 bonates, chlorate, ferrocyanide, and tartrate, and found that 

 all attracted various bacteria (B. termo, Spirillum undula), 

 and the flagellate Bodo saltans with greater or less strength, 

 when the solution in the capillary tube contained 0.1% K. So, 

 likewise, various salts of sodium, rubidium, caesium, lithium, 

 ammonium, calcium, strontium, barium, magnesium, especially 

 the chlorides, were employed. All of these solutions at a 

 concentration of 0.5% exhibited a marked attractive influ- 

 ence upon Bacterium termo ; a weaker one, upon the two 

 other, species. 



Stange ('90) experimented with the action of various phos- 

 phates upon zoospores of a Saprolegnia belonging to the ferax 

 group of De BAEY.f Sodic, ammonic, lithic phosphate, calcic 

 pliosphate held in solution by COg, as well as phosphoric acid 

 were employed and found to act attractively. Other salts, 

 KNO3, K2SO4, KCl, HKCO3, BaClOg, SrCOg, MgSO^, had 

 either a negative or indifferent action upon the zoospores. 



The attractive action of the phosphates is correlated with 

 the fact that phosphates are abundant in the muscles of insects. 

 The following table shows the effect of the different strengths 

 of solutions of four phosphates upon zoospores of Saprolegnia. 

 In this table, constructed from Stange, the symbol r indicates 

 repulsion ; 0, no action ; a, attraction ; a^ indicates a slight 

 attraction ; a^, a strong attraction ; a^r-^, an attraction which 

 is partly balanced by a repulsion due to density, so that the 



* The method employed by Pfeffer in his experiments was as follows : 

 Glass capillary tubes with a lumen of from 0.03 to 0.14 mm. diameter and a 

 length of 7 to 12 mm., and sealed by fusion at one end were employed. To fill 

 the capillai-y tube, it was placed in a watch-glass containing the experiment solu- 

 tion, and the whole was placed in a vessel from which air was pumped. Under 

 the diminished atmospheric pressure, 2 to 4 mm. of fluid entered the capillary 

 tube ; the rest of the tube contained air, which kept the fluid oxidized. After 

 rinsing, the free end of the tube was plunged into the drop culture, whence the 

 solution diffused out. 



t The species were cultivated upon carcasses of flies thrown into glasses filled 

 with bog water. After good colonies were obtained, the carcasses were washed, 

 to rid of Infusoria. Such colonies may be employed to infect sterilized flies' 

 legs placed in sterilized bog water, or they may be transferred directly to wounds 

 in flies' legs. 



