8z8 THE POPULAR SCIENCE MONTHLY. 



These are facts, perfectly well proved, and confirmed by num- 

 berless observations made upon both the leucocytes of higher ver- 

 tebrates and the amoeboid cells of lower organisms. In fact, the 

 whole first part of Metchnikoff's Legons sur l'lnflammation is 

 given to the description of like observations upon the ingestion 

 and digestion of bacteria and other micro-organisms, and these 

 observations are so conclusive that we already see growing a new 

 science comparative pathology which will have to study the 

 diseases and the means of defense against disease in all classes of 

 animals. More than that. Not only those leucocytes which 

 happen to be near to a microbe introduced within the body, do 

 swallow it. It is now certain that as soon as microbes, or even 

 some foreign substance like a splinter or coloring matter, is in- 

 troduced into the body, the wandering white corpuscles of the 

 body immediately move toward the foreign matter or organism, 

 as if they were endowed with a certain irritability or sensibility, 

 which directs their movements. This fact is so usual that Metch- 

 nikoff is even brought to advocate the idea that the distinctive 

 feature of every inflammation is such a gathering of leucocytes 

 around the infected spot, in order to destroy, if possible, the cause 

 of infection. The defense of the living body by means of its 

 phagocytes would thus be a fundamental character of all organ- 

 isms, high and low, acquired and perfected during their evolution 

 under the necessities of struggle for life. 



However, not all bacteria are ingested by leucocytes. Thus, 

 the leucocytes of mice (which so easily succumb to anthrax) do 

 not swallow the anthrax bacilli ; and those of pigeons and rabbits 

 (who succumb to chicken-cholera) do not swallow the bacilli of 

 that special disease. This fact has, however, nothing very as- 

 tonishing in it, as it has its analogy in the life of the lowest 

 organisms. Thus it has been proved that the Plasmodium of the 

 slime-fungi, or Myceiozoa (it occurs as a gelatinous mass on the 

 surface of trees), which consists of numberless nucleated amce- 

 bula?, and creeps by itself over the bark of the trees, most dis- 

 tinctly displays a certain option in choosing the direction of its 

 movements. If cauterized at some spot of the part which moves 

 foremost, it changes the direction of its motion, and leaves the 

 cauterized spot behind. A decoction of dead leaves attracts it, 

 while a solution of sugar or salt repels it.* The same is known 

 of isolated amcebse. So also the leucocytes immediately attack 

 and ingest some microbes, living or dead, but avoid some others, 

 and various kinds of leucocytes behave in various ways. The 

 mono-nuclear leucocytes of man seem loath to attack the bacilli 

 of erysipelas, while the many-nuclear ones display no such re- 



* Metchnikoff's Lecjons sur l'lnflammation, pp. 38 et seq. 



