1907.] Complement-content of Fresh Blood-serum. 381 



Investigated in a number of the normal serum experiments. A portion 

 of the first sample was set aside in the cold after centrifuging, and examined 

 some hours later, at the same time as a sample which had remained on the 

 clot during the same period. The results show that a rise does occur in 

 the serum, even when separated from the clot. The amount of this rise is, 

 however, very small, only a small fraction of the increase which has taken 

 place in the serum left on the clot. E.g., in the example given above, the value 

 of the 20 minutes sample rose in five hours, when off the clot, from 0*3 c.c. only 

 to 0-2 c.c, as against the rise to 0*08 c.c. of the serum left on the clot during 

 that time. It is not easy to suggest an explanation of this phenomenon. We 

 might suppose that complement exists in serum or plasma partially in an 

 inactive or zymogen phase, which is slowly converted into the active body. 

 Or again, on the view that complement is derived from leucocytes, we may 

 suggest that even after prolonged centrifugalisation, fragments of white cells 

 remain suspended in the serum and gradually disintegrate. Such explana- 

 tions, however, have as yet no real experimental basis, and we know too little 

 of the nature and source of complement to make speculations profitable. 



In the normal sera examined, then, hemolytic complement increases by 

 100 to 200 per cent, during the first few hours after the drawing of blood, the 

 duration of the increase extending in the case of the rabbit over a period of 

 five to seven hours, in the case of the guinea-pig over a period of two to 

 four hours. It is probable that this variation is not peculiar to the hemolytic 

 complements. Ainley Walker (1) found the bactericidal action of serum to 

 increase during the first few hours after the blood was shed, and attributed 

 this to an increase in the amount of complement. According to Macdonald (2), 

 whose results have been confirmed by Craw, the opsonic power of serum 

 undergoes a similar increase. 



J. H. Craw has pointed out that all these bodies are relatively unstable, 

 while the hemolytic immune-body, which does not vary, is comparatively 

 stable ; but whether this fact is of significance can only be determined when 

 further evidence has accumulated on the subject. The results obtained in 

 the experiments recorded here have no immediate bearing on MetehnikofFs 

 view that alexine does not exist as such in circulating plasma. Sufficient 

 serum for examination does not separate until 15 to 20 minutes have elapsed 

 from the time of bleeding. In the serum then obtained the amount of 

 complement, though much less than is found later, is still always considerable, 

 and there was nothing to indicate that at the moment of bleeding the blood 

 contained no active complement. « 



Example 2. — Dose of immune-body : 0*025. Horse red blood-corpuscles : 

 4 c.c. of 1-per-cent. suspension ; two hours at 37°. Quantity of normal 



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