FURTHER DEVELOPMENT OF KNOWLEDGE 177 



such reactions is, they claim, its rapid deterioration at 37 to 40 C., 

 when diluted. If they are right, these considerations also remove 

 important objections to the conception of complement as a ferment. 



It is clear, therefore, that although we have gained much detailed 

 information regarding the functional activity of the complement or 

 alexin, and may assume, in a general way, that its action is similar 

 to, if not identical with, that of an enzyme, we are nevertheless still 

 very much in the dark concerning its chemical nature. The same 

 thing may be said in regard to its physical characteristics. One 

 method of investigating the physical properties of complement has 

 been that of filtration. It may be remembered that one of Ehrlich 

 and Morgenroth's 41 arguments in favor of the multiplicity of com- 

 plement was the fact that, when goat serum was filtered through a 

 Pukal candle, the complement which was active upon rabbit corpus- 

 cles was retained, while that which acted upon guinea-pig cells 

 passed through. Immune bodies or amboceptor always passed 

 through. 



Vedder, 42 in similar experiments upon bactericidal complements, 

 claims to have been able, in the same way, to separate the comple- 

 ments acting upon different bacteria. The problem has been more 

 recently investigated by Muir and Browning. 43 Their conclusions 

 are briefly as follows: In the early stages of filtration through a 

 Berkefeldt filter complement is often completely held back. After 

 continued filtration it begins to pass through. If the complement is 

 inactivated by the addition of hypertonic salt solution (5 per cent.), 

 it passes through, and the filtrate can be reactivated by dilution to 

 isotonicity. Sensitizer or amboceptor always passes through. Just 

 how these experiments are to be* interpreted is a little obscure. The 

 fact that the addition of salt renders the complement capable of 

 passing through the filter would seem to indicate that its original 

 inability to permeate did not depend upon the size of the molecule. 

 On the other hand, it is also possible that the addition of salt to the 

 complement may increase its dispersion in such a way that the indi- 

 vidual particles are rendered smaller. This, however, is purely 

 speculative, and we are at a loss for a fully satisfactory explanation of 

 the results of Muir and Browning. We have repeated some of the 

 experiments of Muir and Browning and, in substance, 'confirmed 

 their results. It is our opinion that new filters remove complement 

 by adsorption, just as this is accomplished when complement is 

 shaken up with kaolin or other finely suspended material. 



That the addition of salts of various kinds in quantities greater 

 than isotonicity (or more than the equivalent of 0.85=0.9 per cent. 



41 Morgenroth and Ehrlich. Ehrlich's "Gesammelte Arbeiten," etc. 



42 Vedder. Journ. Med. Ees., Vol. 9, 1903. 



43 Muir and Browning. Journ. of Path, and Bact., Vol. 13, 1909. 



