THE LEUCOCYTES IN ORGANIC FUNCTIONS. 677 



important role in the mutual relations of these lowly organ- 

 isms. Many rhizopoda and infusoria live in media swarming 

 with other unicellular organisms, including bacteria. The 

 latter, which multiply very rapidly, serve as food to many of 

 the protozoa. Thus, various amoeba? devour bacilli, which un- 

 dergo certain definite changes in the interior of the protoplasm. 

 Without altering their shape, the bacilli acquire the power of 

 taking up solutions of vesuvine, which does not stain these 

 microbes when living in their material conditions. Since pre- 

 cisely similar changes are also observed in the interior of vorti- 

 cellse and infusoria, which live on bacteria, it is evident that 

 they are due to a digestive influence exerted by the contents 

 of the protozoa." This conclusion is in harmony with the ob- 

 servation of B. Hofer 9 on digestion in amoebae. This investi- 

 gator has shown that "the more the food is altered in the in- 

 terior of these rhizopods, the more easily does it stain with 

 aniline dyes." When we consider that aniline dyes include 

 methylene-blue, we have evidence, in view of Ehrlich's observa- 

 tion that the "conditions essential to the methylene-blue reac- 

 tion" are "oxygen saturation and alkalinity" that the proto- 

 type of amoeba, the leucocyte, must owe its nuclear functional 

 activity to the plasma as exogenous reagent. 



Metchnikoff further says: "We may often see flagellated 

 monads taking up filaments of leptothrix several times as 

 long as themselves, and finally inclose them in their digestive 

 vacuoles." The process of ingestion is beautifully shown in 

 the plate opposite page 628, in Figs. 19 and 20, the organisms 

 here being spirilla of Asiatic cholera. "It is sometimes possible 

 to follow all the changes undergone by the bacteria within an 

 infusorium," continues the same investigator, "as is the case 

 of the digestion by stentor of the sulpho-bacterium thiocystis, 

 observed by le Dantec." 10 . . . "It is evident that the di- 

 gestive function of the protoplasm of the protozoa must hinder 

 the invasion of these animals by the lower organisms, and it is 

 only in certain special cases that the latter can live as parasites 

 within the rhizopoda and infusoria." 



The true identity of the perinuclear vacuole seems fur- 



9 B. Hofer: Jenaische Zeitschrift, vol. xxiv, 1889. 

 10 Le Dantec: "Recherches sur la digestion intracellulaire," Lille, 189L 



