10 



and di Mattei,* had, some months previously, argued that the rapidity 

 with which the injected micrococci of swine erysipehis disappear from 

 the blood is evidence that there can be no question of phagocytic action^ 

 and that therefore there must be some anti-bacterial substance developed 

 by the cells of the body and free in the humours. 



There is not space here to give in detail Metchnikoff's very able 

 refutation of the argument of Emmerich aud di Mattei ; suffice to say 

 that using still smaller quantities of the virus than did these observers, 

 and employing refractory and not susceptible animals, thus again making 

 his case stronger, Metchnikoif showed that in place of the microbes being 

 all destroyed in from fifteen to twenty minutes some at least were still alive 

 aud capable of giving cultures after several hours, indeed for as long a 

 period as four days, and he found that in two and a half hours there was 

 already definite phagocytosis obsei-vable, some phagocytes containing as 

 many as twenty-eight bacilli, f 



These observations and others of a similar nature showed conclusively 

 that outside the body the humours have an unmistakable power of 

 destroying many forms of micro-organisms. The next question to be 

 determined in order to establish the humoral theory was whether any 

 relationship is to be made out between the insusceptibility of an animal 

 to a given disease, and the degree of bactericidal power of its body 

 fluids. 



It was discovered, in the first place, that the different fluids of the 

 body possess bactericidal powers differing in degree. Thus, f jr example, 

 the blood serum is generally speaking the most active of all, the aqueous 

 humour the least active. But the fact is not opposed to the humoral 

 theory, for in the susceptible animal it requires a larger injection of 

 pathogenic microbes into the circulation to induce disease than is 

 required in the case of inoculation into the anterior chamber of the eye. 

 At the same time, the fact that the aqueous humour is deficient in 

 leucocytes, while the blood contains them in quantity, makes this argu- 

 ment support the phagocyte theory equally well. It is when we attempt 

 to solve the problem more directly that the humoral theory is found to 

 be insufficient, and we owe to those who first propounded the theory the 

 most striking demonstrations of its insufficiency. Thus Nuttall showed 

 that the blood serum of the susceptible rabbit is more bactericidal 

 towards the anthrax bacilli than is that of the sheep which has been 

 rendered immune, and Behring and NissenJ pointed out that the same 

 micro-organism develops without delay in the serum of such refractory 

 animals as fowls, frogs, cats, and sheep that have been rendered immune, 



* Emmcricb and di Mattei. — Fortschritte der Medkin, VI. p. 720. 



+ " In the torpedo, injecting anthrax bacilli, Lubarsch found phagocytoo after three quarters 

 of an Iiour in pretty nearly every preparation he made, many phagocyteB containing from 20 to 

 30 bacilli."— «i(. /. Bakt., Vol. VI., 1SS9, p. 630. 



X Behring and Nissen.— Zdtsc/if./. Hygiene, Vol. VIII., 1890, p. 421. 



I 



