BACTERIOLYSIS AND ALLIED PHENOMENA 185 



fortunate that the evidence in its favour is clear and direct ; and it 

 may be added that the proof is strengthened by the demonstration 

 of the fact that the agglutinins are formed in the same region. It 

 seems clear that the main, if not the only, function of the lympho- 

 cyte is the elaboration of the defensive antibodies. 



There is no doubt that immune body, like the other antibodies, 

 circulates as such in the plasma. The most striking proof is that 

 of Metchnikoff in regard to spermotoxin, but other evidence is 

 available, and the point is not disputed. 



Methods of Researches on Immune Bodies and 

 Complements. 



The methods employed in the investigation of the haemolytic 

 sera are fairly simple in theory, though, as a rule, somewhat 

 tedious in practice, owing to the necessity, in most cases, for 

 quantitative work (so that slight degrees of haemolysis may not be 

 overlooked), and for numerous controls. The animal used in the 

 preparation of the immune serum will naturally depend on the 

 corpuscles to be employed, but in most cases the rabbit is most 

 convenient. The corpuscles used for immunization should be 

 collected in normal saline solution containing about i per cent, 

 sodium citrate, centrifugalized, and rewashed three or four times 

 in normal saline solution, so as to remove every trace of serum, 

 complements, etc. If this is not done the resulting serum may be 

 of great complexity, and results obtained by its action misleading. 

 The emulsion used for the injection may contain about half its 

 volume of corpuscles, and some 10 c.c. (or more in the case of 

 large rabbits) may be injected into the peritoneum. In most 

 cases three such injections at weekly intervals will cause the pro- 

 duction of a powerful haemolytic serum, but if there is any doubt 

 5 c.c. or so of blood may be withdrawn from the marginal vein of 

 the ear, and used to test the progress of the immunization. The 

 ear is well rubbed to make it hyperaemic, shaved, and washed with 

 alcohol. A small puncture is now made with a flat surgical 

 needle or fine knife, taking care that the vessel is merely incised 

 and not completely divided. As a rule the blood will now flow 

 quickly, drop by drop, and a sufficient amount may be collected in 

 a sterile test-tube. If the flow is sluggish the blood may be 

 milked out by passing the finger gently along the vein. 



When the immunization is complete the rabbit is usually killed, 

 and as much blood as possible is collected. The best way to do this 



