1904.] On Chemical Combination and Toxic Action, etc. 301 



complement taken up depends upon the firmness of union of comple- 

 ment, and has been described in former papers.* 



I. Immune-body to Guinea-pig's Corpuscles (obtained by injecting the 

 Rabbit with these corpuscles). 



(a) With Guinea-pig's Complement 



We may first compare the results when guinea-pig's complement is 

 used, with those when rabbit's complement is used. In the former 

 case the dose of complement is very high ; in fact, more than ten times 

 the amount of guinea-pig's complement sufficient to hgemolyse ox's 

 corpuscles, is necessary to haemolyse its own corpuscles. This might 

 be due to the fact that only a fraction of the complement molecules 

 suited the immune-body to guinea-pig's corpuscles, or it might be due 

 merely to weakness of toxic action of the complement. If the former 

 were the case the presence of the uncombined complement would be 

 shown by adding the corpuscles of another animal treated with the 

 corresponding immune-body. The matter is put to the test by adding 

 varying amounts of guinea-pig's complement to guinea-pig's corpuscles 

 with their corresponding immune-body, and then after allowing 

 2 hours at 37 C. for combination, to test for the presence of comple- 

 ment by means of ox's corpuscles treated with their immune-body. If 

 we use 1 D of immune-body to indicate the amount necessary to 

 produce lysis when rabbit's complement is used, then 10 D will 

 be the M.H.D. when guinea-pig's complement is used. The following 

 are the chief results which we have obtained. It is to be noted that, 

 of course, if less than 10 D is added complete lysis does not occur 

 with guinea-pig's complement, and in such cases the tubes are cen- 

 trifugalised and the clear fluid is added to the indicator, i.e., ox's 

 corpuscles treated with their immune-body. This indicator is 

 specially suitable on account of the high sensitiveness of the corpuscles 

 to guinea-pig's complement. 



Such an experiment may be graphically represented thus 



Guinea-pig's Q+nlB -\- x guinea-pig's C \ + Ox's Q + IB 



the small circle indicating red corpuscles, the vertical dotted line 

 a period of incubation at 37 C., n indicating a definite multiple of 

 IB, and x varying amounts of C. 



* Muir, ' The Lancet,' 1903, vol. 2, p. 446 ; and Muir and Browning, ' Roy. Soc. 

 Proc.,' June 9, 1904. 



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