266 IXFLAMMATION, REGENERATION, GROWTH 



disiiitegratiou of the leucocytes. Lymphocytes and macrophages seem 

 to be devoid of this endolysin.'^^ 



Phagocytosis of living virulent bacteria may not always be an un- 

 mixed benefit. Besides the obvious pos.sibility of transporting the 

 bacteria and spreading infection, we have also evidence that living 

 bacteria may be protected through phagocytosis, against the action of 

 bactericidal substances in the blood and tissues (Rous and Jones) ."^ 



THEOEIES OF CHEMOTAXIS AND PHAGOCYTOSIS 



On the assumption that leucocytes obey the same laws in their mo- 

 tions as do the ameba?, studies of the latter and of other forms of 

 protozoa have furnished most of the ideas, hypotheses, and theories 

 of the forces involved in leucocytic activities. The structural rela- 

 tion of the leucocyte to the ameba is striking, although by no means 

 complete; the relation of their activities is even closer. Each is a 

 microscopic, independent, unicellular organism, moving freely in all 

 directions by means of pseudopodia and protoplasmic streaming, 

 taking other smaller bodies into its substance and digesting them, 

 reacting similarly to like stimuli, and containing similarly a nucleus 

 and many granules. The differentiation of the protoplasm of the 

 ameba into a clear outer ectosarc and an inner granular endosarc is 

 perhaps an important difference, but so far as the two forms of cells 

 have been studied, the elTect of this difference in structure does not 

 seem to have been considered. That the unicellular protozoa, devoid of 

 any central nervous system, and without any apparent co-ordinating 

 mechanism, seem able to move about in a purposeful way, going toward 

 food supplies and away from injurious agencies, toward or away from 

 light, heat, and chemicals, has long attracted the interest of physi- 

 ologists, particularly as in these single-celled organisms w^e may look 

 for the simplest conditions of existence and the most elementary life 

 processes. It seems absurd to imagine that a paramaecium goes toward 

 a dilute acid because it "likes it," that an ameba rejects a piece of 

 glass because it "does not taste good," as we explain similar nuuii- 

 festations in higher forms ; furthermore, it has been shown by Verworn 

 that minute enucleated fragments of protozoan cells react to stimuli 

 just as does the entire cell, and, therefore, it seems that the only possi- 

 ble explanation of movements in protozoa must be a direct reaction 

 of the stimuhited part to the stimulus. The luiture of the stimulus 

 and the nature of the stimulated substance must determine the nature 

 f)f the resulting reaction, and most of the observations so far made 

 suggest that these reactions can be explained according to the known 

 law^s of tlie physics of fhiids. An ameba, or a leucocyte, may be lookeil 

 upon as a di'oj) of a colloidal solution, surrounded l)y a delicate sur- 



M Sco Schneider, Arch. f. Tlvpr., 1000 (70), 40. 

 sia.Iour. Exper. Med., lOlG (23), GOl. 



