18 ROYAL SOCIETY OF CANADA 



protonuclein has, at least clinically, no effect in combatting infectious 

 disease. At most, certain experiments of Durham's (Journ. of Path, 

 and Bacter., lY., 338, 1897) serve to indicate that a local leucocytosis 

 (as, for instance, on the omentum in cases of peritonitis) on occasion 

 may, for a time at least, restrain the advance of infective agents, mainly, 

 as it would appear, from the mechanical hindrance presented by the 

 accumulated cells. Then, again, it has been abundantly proved that 

 the blood serum is not bactericidal, or even inhibitory, for all germs, 

 .while there are noteworthy differences between the sera of various races 

 of animals in regard to their destructive powers upon bacteria. Now, 

 as we have seen, " Dust-bodies " are to be found in the blood serum of 

 a considerable number of animals, and if they were the source of the 

 bactericidal properties of the blood, we would not expect to find these 

 differences. E^ddently, the " Dust-bodies " must possess different pro- 

 perties in different animals, or else there are other factors to be taken 

 into account. The available evidence all goes to prove the ' general 

 uniformity of the process of immunity induction, at least in the warm- 

 blooded animals. The defensive action of the leucocytes would appear 

 to depend, not so much on an external liberation of substances from 

 their protoplasm, as on their power of ingesting and digesting bacteria 

 and other foodstuffs. This phagocytic power seems, however, to depend, 

 according to some recent experiments of Wright and Douglas (Proc. 

 Eoyal Soc, Vol. 72 and 73), on some peculiar quality in the serum, 

 which they term the " opsonic " property. The interdependence of leu- 

 cocytes and serum is most interestingly and conclusively shewn in their 

 studies. The bactericidal properties of the blood have been attributed 

 by Buchner to the presence in it of certain labile, chemical substances, 

 which he calls "alexins" ("defensive proteids" of Hankin). These 

 are believed by Kossel and Vaughan to be derivations of nuclein or 

 nucleinic acid, while Hankin thinks that they are due to solution of 

 eosinophilic granulations in the plasma. If Hankin's view be correct, 

 one would suppose that liberated granulations would rapidly disappear, 

 but on keeping fresh blood, as we have seen, the " Dust-bodies " actually 

 increase, so that, from Stokes and Wegefarth's view point, either Han- 

 kin's theory of immunity is wrong or else the " Dust-bodies " are not 

 free granulations, and in either case their contention falls to the 

 ground. The fact that the antitoxin of one disease does not protect 

 against the ravages of another would indicate that there are specific 

 differences in the method of immunity production in certain cases, 

 differences which cannot be explained by so simple a theory as that 

 advanced by Hankin and accepted by Stokes and Wegefarth. The 

 manifold nature of the problem is sufficiently evident and its solution 

 is not yet. 



