THE PRESENT POSITION OF ANTISEPTIC SURGERY 333 



some of his experiments. The green frog, below tlie temperature of 20° C. 

 (68° Fahr.) is incapable of taking anthrax : the bacilli of that disease cannot grow 

 when introduced under the skin of that animal. To what was this immunity of 

 the frog to anthrax due ? Were its juices an unht pabulum for the microbe, or was 

 the phagocytic action ol its leucocytes the explanation ? In the hope of solving 

 this question, Metchnikoff formed a tiny bag out of the pith of the reed, and 

 having placed in it some spores of anthrax, closed the bag and inserted it beneath 

 a frog's skin. The pith wall of the bag allowed the animal's lymph to penetrate 

 by diffusion, but excluded the leucocytes : and the result was that the spores 

 sprouted and grew into luxuriant threads of anthrax in the lymph, which was 

 thus proved to be a suitable medium for the growth of the bacillus. Meanwhile 

 under another part of the skin of the same frog had been placed a small piece 

 of the spleen of an animal that had just died of anthrax and contained the 

 microbe in its most virulent form ; but there, the leucocytes having free access, 

 no growth occurred. 



Another experiment on the same principle was still more instructive. It 

 consisted in introducing the spores of anthrax into the anterior chamber of the 

 eye of a frog, which, as we have seen, is naturally insusceptible of the disease ; 

 and also into that of a sheep and of a rabbit rendered insusceptible artificially 

 by ' vaccination ' with Pasteur's attenuated virus. The aqueous humour of the 

 healthy eye contains few if any leucocytes to interfere with the perfect trans- 

 parency essential to vision. Accordingly, the spores sprouted and grew for a 

 while freely in the anterior chamber. Meanwhile, the growth of the bacillus 

 occasioned irritation to the eye, resulting in the immigration of a constantly 

 increasing number of leucocytes, producing turbidity and, in time, hypopion. 

 If a drop of the aqueous humour was withdrawn at an early period after the 

 commencement of the experiment, and examined with the microscope, it was 

 found to contain anthrax bacilli, some of them free in the liquid, but others 

 enclosed in the bodies of leucocytes. But a drop taken after a longer period 

 had elapsed showed no free bacilli, all being now within the leucocytes, and 

 exhibiting signs of degeneration in various degrees as the result of their ad- 

 vancing digestion. Finally tlie anthrax disappeared entirely and the eye 

 cleared up, the animal in all cases remaining healthy, although inoculation into 

 the aqueous humour i)rovcd a peculiarlv deadlv mode of infecting a susce]')tible 

 animal.^ 



Here we see that the inflammation excited by the microbe becomes, through 

 the medium of the leucocj^tes, the cause of its destruction. How little can the 

 lamented Cohnheim have dreamed that his observation of tlie emigration of 



' See Annates dc I' Institnt Pasteur, 25 juillct, i^^j, pp. 3-O, ^zj. 



