the contrary, move?, at lust, towards tho li(iuiil, just as it does i»rimarily 

 in tho cnso of tho drop of iufusion of oak bark. 



Passing over certain observations of do liary we como to numerous 

 researches made since 1885, by W. Pfoffor, to whom espoci'illy we owo 

 our knowledge of chemiotnxis among the lower plant furms ; wiiile 

 equally important though not so extensive aro tho researches of Rosen, 

 who pointed out that tho spores of C'lytridium zygnomatis are attracted 

 by the prockicts of decomposition of tl o cells of Zygnema ; of Zopf, upon 

 the attraction of zoospores of certain Chytridiacea) towards poUon grainn, 

 and of Stange upon tho cheralotactlc movemouts of Myxomycetes and 

 the zoospores of Saprolegnia. 



Pfeffer showed that certain substances exert an almost specific action 

 upon some vegetable organisms; that, for instance, malic acid has a 

 remarkable attraction for the seminal filaments of ferns and solaginoUais ; 

 that nutritive media exert a similar action upon motile bacteria ; and, 

 again, that this chemiotaxis is determined by the specific chemical nature 

 of the substance, and not by movements of diffusion of tho liquid. 

 Continuing his observations upon chemiotaxis in connection with bac- 

 teria, ciliate infudoria and volvocinete, Pfeffer made out that a positive 

 chemiotaxis is exerted by peptone (energetic), asparagin, creatin, taurin, 

 sarcin, carnin, urea (feeble), dextrin, and for certain organisms (and here 

 to a high degree), glucose; also in another class of substances by sali- 

 cylate of sodium and morphine; while a negative chemiotaxis occurs 

 with free acids, alkalies and salts (lactate of iron and zinc sulphate). 



If then the lowest organisms exhibit such chemiotactic properties, 

 it became a matter of considerable interest to observe whether, by using 

 similar means, like peculiarities could be determined for the leucocytes — 

 cells whose every property finds its counterpart among those possessed 

 by the amoeboid animal and vegetable organisms. The first definite 

 observations made in this direction were those of Pekelharing in 1889.* 

 Introducing under the skins of frogs small masses of cotton wool, some 

 moistened with indifferent fluids, others with anthrax cultures (the frog 

 being refractory to anthrax), and removing these after some hours, 

 Pekelharing found that tho wool impregnated with the bacilli contained 

 very many more leucocytes than did that steeped originally in indifferent 

 fluids. A few months later, in February, 1 890, Massart and Bordetf pub- 

 lished what is really the first, as it is tho most important, systematic re- 

 search upon the excitability of the leucocytes. These observers employed 

 what was essentially Pfeffer's method, and what was, it may be noted, but 

 a modification of that introduced some years ago by Councilman to deter- 

 mine an allied question, namely the formation of pus by irritants, such 



* Pekelhnrlng. La Smaine Mhlieale, No. 22, 1880, p. 184. 



+ Massart et Bordet. Journal de la Societc KoyaU, des Science! MedicaUt et Katuralea de Bruxdles, 

 18!)0. 



