1907.] Complement-content of Fresh Blood-serum. 385 



change which it shows to occur is, however, more open to question. It is 

 assumed that the immune-body undergoes no alteration in the process of 

 heating, and this, probable as it may be, has not been proved. Further, the 

 existence of different proportions of partial complements in the two sera 

 would affect the quantitative accuracy of the results obtained. In any case, 

 great stress should not be laid on particular figures, since the experimental 

 error is quite appreciable, though remarkable regularity and accuracy are 

 obtainable with hemolytic sera. While we may rely, then, on the method 

 showing us whether any change occurs, and the duration of such change if 

 present, the amount of change indicated is probably only an approximate 

 measure of what really occurs. 



In example No. 5 given above, the amount of complement had risen by 

 the end of one hour to double the amount first observed. As a rule, the 

 increase is rather less. In some of the experiments (10 were made with 

 immune sera) no increase at all was found, the complement diminishing 

 steadily from the first observation. Further, in all the experiments where 

 any rise took place it was complete in one and a-half to two hours after the 

 blood was drawn. 



There is a difference, therefore, between normal and immune serum in this 

 respect. In normal serum we found the complement to increase by 100 

 to 200 per cent, and the duration of the increase to be from five to 

 seven hours. In immune serum the full amount of complement is often 

 present from the first, and where an increase does occur, it is complete in 

 a short time and is not so great as the increase in normal serum. By the 

 process of immunising, therefore, complement, or the source of complement, 

 has been altered in such a way that it is developed in the serum with 

 greater readiness than is the case with normal blood. The repeated 

 injections of red cells may have induced repeated new formations of 

 complement, with the result that the leucocytes or other cells have been 

 " educated," in Metchnikoff's sense, to secrete complement, or its precursor, 

 more quickly than where such stimuli have not been given. But here, again, 

 explanation becomes pure hypothesis. 



On the suggestion of Professor Muir, an experiment was made to see 

 whether the change produced by the process of immunising affected all the 

 hemolytic complements of the animal immunised or only those specially 

 concerned in the laking of the reel cells used for the immunisation. A rabbit 

 immunised against ox corpuscles was bled, and samples of serum withdrawn 

 in the usual way. Two series of experiments were then carried out. In 

 the first, ox corpuscles and the appropriate immune-body were used, and the 

 variation of the complement determined by the method for immune serum. 



