4 Prof. R Muir and Mr. C. H. Browning. [May 17, 



1. C of guinea-pig ; M.H.D. = 0'03 c.c. 



Anti-C to guinea-pig's C obtained by injecting a rabbit with guinea-pig's serum. 



To each of a series of tubes containing 0'5 e.c. salt solution O'l c.c. anti-C is added, 

 and to the several tubes 0'03, 0'04, 0'5 c.c., etc., of guinea-pig's C is added. The 

 tubes are placed in the incubator at 37 C. for an hour. 



The amount of C obtainable in each tube is tested by adding to each 1 c.c. 

 suspension of red corpuscles, treated with IB, and incubating for an hour, the 

 tubes being afterwards placed in a cool chamber for 16 hours. 



It is found that in the tube containing 0*03 c.c. C a mere trace of 

 lysis has occurred, in the tube 0'04 c.c. C half the corpuscles have 

 undergone solution, but it is not till the tube containing 0*12 c.c. C is 

 reached that complete haemolysis of the corpuscles has occurred. In 

 other words, if we take the tube where C is first obtainable from the 

 mixture of C and anti-C, three additional doses of C must be added 

 before a full haemolytic dose is obtainable. 



2. In this case 0'05 c.c. anti-C is used, and the M.H.D. of C is 0'05 c.c. The 

 procedure is the same as before. The result is that even from the tube containing 

 0'03 c.c. of C a trace of C is obtainable, but a full hsemolytic dose is got first in the 

 tube containing O'l c.c. of C, i.e., one-and-a-half hsemolytic doses must be added ere 

 one remains free. (It is to be noted that here the amount of anti-C is only half of 

 what it was in the previous case,) 



Such results, which agree with those of Bordet, clearly show 

 that with a mixture of C and anti-C there is no sharp line of 

 neutralisation. On the contrary, even with relatively small amounts 

 of C and anti-C, if we determine the point at which C is first 

 obtainable, then several doses of C must be added before a full 

 dose is obtainable. We have avoided using the term "free C " 

 with reference, to the C which is obtainable from such mixtures, 

 because we believe that part of the C is got by dissociation. Of 

 this there is distinct evidence. In every case where red corpuscles 

 treated with IB are added to a mixture of C and anti-C, and complete 

 lysis has not occurred, it is found that after the corpuscles have been 

 allowed to settle, a zone of diffusion of haemoglobin is seen above the 

 sedimented corpuscles. This is evidently to be explained on the 

 supposition that in such a tube there is, in addition to the combined C> 

 a minute trace of free C. This latter combines with the red corpuscles, 

 and according to the law regarding substances loosely combined, a 

 small quantity of C is dissociated from the combination C + anti-C to 

 take its place. This process is repeated during the sedimentation 

 of the red corpuscles, and the result is an additional amount of 

 solution of haemoglobin. Such a phenomenon is not seen in ordinary 

 test-tube experiments, where there is incomplete lysis with a mixture 

 merely of C and IB. It follows from what we have said that we 

 consider it to be impossible to determine by such methods the exact 

 point at which C remains free in a mixture of C and anti-C we can 



