12 STUDIES IN IMMUNITY. 



organism against infection. It is certain that positive chemiotaxis 

 of leucocytes has been proved in an exact manner by demonstrative 

 experiments that cannot be controverted. Bacterial cultures 

 attract leucocytes, and this attraction is often very marked. This 

 is an established fact, the significance of which from the standpoint 

 of immunity appears quite evident. Let us hasten to add that 

 Woronin does not deny chemiotaxis; but he thinks that this re- 

 action on the part of the leucocytes is not indispensable nor even 

 particularly useful to them. Phagocytes may, according to this 

 author, fulfil their function simply by means of their tactile reaction. 

 This investigator attempts to show anew the already well known 

 fact that leucocytes do react to contact, that they voluntarily enter 

 porous bodies, openings in tissues, etc. He recognizes that the 

 reaction to contact is very highly developed and concludes that the 

 engulfing of bacteria may be due simply to this reaction. No one 

 doubts that the tactile reaction is a valuable property in leucocytes, 

 as is made clear by those authors who have studied chemiotaxis.* 

 It appears quite certain that phagocytes, when they open up on 

 contact with inert non-attractive particles (charcoal, for example), 

 may ingest them in their protoplasm ; this ingestion is due entirely 

 to the tactile sensitiveness of the cells. But how does the import- 

 ance of the leucocytic reaction to contact diminish the reaction to 

 chemical substances? How much must the taking-up of living or 

 dead particles be facilitated if these particles diffuse substances 

 that attract leucocytes and cause them to move toward the particles? 

 If we admit the intensity of positive chemiotaxis, which is easily 

 determined, we cannot deny to these phenomena their evident 

 function. Werigo 's objections f to the arguments which tend to 

 admit a negative chemiotaxis of leucocytes are better founded. 

 Werigo does not think it has been shown that there are substances 

 capable of producing a retraction of leucocytes. We have been 

 accustomed to regard lactic acid, for example, as possessing such a 

 repellent action from the following experiment: if we mix a small 

 quantity of lactic acid with substances which are very attractive 

 (bacterial products), it is noted that the mixture no longer attracts 



* J. Massart and C. Bordet., loc. cit. 



f Werigo, De"veloppement du charbon chez le lapin. Annales de 1'Institut 

 Pasteur, 1894. 



