52 STUDIES IN IMMUNITY. 



tainly another factor that affects it, namely, the condition of the 

 capillary walls.* Issaeff has already shown that a substance with no 

 chemiotactic influence, namely, normal salt solution, when injected 

 into the peritoneal cavity, increases the number of cells there. 



Definite information then may be obtained by placing the sub- 

 stance to be studied within capillary tubes closed at one end and 

 leaving these tubes in the peritoneal cavity for several hours. 



If the fluid in such tubes is a good culture medium, careful 

 asepsis must be practised. After the tubes are examined under 

 the microscope their contents may be taken out and spread on a 

 slide. With suitable stains the types of leucocytes present may be 

 noted and also the presence of any micro-organism. The phenomena 

 of attraction which might be attributed to the serum may be due 

 to bacterial secretion, and so it is well when testing the chemiotactic 

 property of a given fluid to place in the peritoneal cavity, at the 

 same time, tubes containing a fluid of which the chemiotactic 

 properties have already been determined. 



EXPERIMENT 16. (a) Four small bundles of tubes were placed 

 in the peritoneal cavity of a normal mouse at 6 P.M., and withdrawn 

 18 hours later. Ether anesthesia was administered during the 

 opening of the peritoneum and placing the tubes. The following 

 table shows the effect of the fluids employed on the leucocytes. 



No. 1. Twenty-four hour agar culture of the Massaouah vibrio 

 suspended in salt solution and sterilized at 100 degrees. Strongly 

 attracting for leucocytes. 



No. 2. Serum of a rabbit vaccinated against the vibrio Mas- 

 saouah; this serum is powerfully preventive and bactericidal. 

 Distinct attraction for leucocytes. 



No. 3. The same serum heated for an hour to 70 degrees (no 

 longer bactericidal but still preventive). Distinct attraction for 

 leucocytes. 



No. 4. Salt solution of 0.65 per cent. No attraction for leucocytes. 



In the tubes containing the sterile cholera culture the leucocytes 

 form a thick plug not extending very far into the tube. In the tubes 



* It has already been shown that leucocytes approach certain substances owing 

 to a reaction to chemical substances, but it has not been proved that this chemio- 

 tactic influence is sufficient to affect leucocytes through the vessel wall and cause 

 their emigration. It may be that chemiotaxis is of importance only after the 

 leucocytes have passed through the wall of the capillary and into the tissues. 



