572 Microscopic Organisms in Blood and their Relation to Disease, [part hi. 



able to induce fatal charhoii by inoculating animals with bacteridial blood without 

 obtaining any bacteridia* in the blood of the animal thus affected, although the latter 

 (bacteridia-free) blood had also induced the disease, and, moreover, given rise to 

 bacteridia in the third animal, although none had been present in the second. 

 Others, again, maintained that the disease was not due solely to contagion, but was, 

 somehow, dependent on the soil, seeing that the disease was only endemic in moist, 

 swampy districts, valleys and sea-coasts ; and that the mortality was greater in rainy 

 years, and especially during August and September, months in which the temperature 

 of the soil reached its highest. The circumstances could not be explained on Davaine's 

 supposition that the organisms, retaining their vitality for a long time in dry air, 

 were conveyed by air currents, or that inoculation was effected by insects, and so 

 forth. Koch's experiments led him to believe that Davaine's explanation of the 

 mode of propagation of the disease is only partially correct. He found that 

 bacteridia-staves were not so hardy as Davaine had supposed. Blood which contains 

 only rods will retain its property in the dry state for but a few weeks, and when 

 moist only for a few days. How, therefore, could the contagion remain dormant in 

 the soil for months and years? If bacteridia had anything to do with the matter, 

 it must be assumed that during some stages of their development they were inert, 

 or that, as Cohn had suggested,! resting spai^es were formed which had the power of 

 retaining their vitality for a long time, and of giving rise anew to bacteridia. The 

 existence of such spores is what Dr. Koch believes he has been able to demonstrate. 

 As this question is a very important one, it is necessary that the evidence adduced 

 should be submitted to careful examination. 



The experiments of Davaine and others were repeated, mice having been found 

 to furnish the most satisfactory results. The tail was seized, and a small portion 

 of its skin being abraded, a drop of the fluid containing the bacilli was placed 

 in contact with the small wound. Such inoculations proved to be invariably fatal 

 when fresh material was used. In order partly to ascertain whether the bacilli passed 

 into some other form by successive inoculations, and also to provide himself with a 

 constant supply of fresh material, he inoculated one mouse after another, the last 

 mouse supplying the material for its successor, until eventually a series of twenty 

 'noculations had been conducted : consequently twenty crops of bacilli had been 

 cultivated without any marked change in their character being noticeable.^ The 

 pathological results were always of the same character — enlarged spleen, and motionless, 

 translucent bacilli (Fig. 39). The latter in mice were more numerous in the spleen 

 than in the blood, but different animals showed different results as regards their 

 distribution in the tissues — the blood of inoculated rabbits, for example, being often 

 so free from them as to be traced with difficulty, though the spleen and glands 



* Cohn's Beitrdge, Band II, Heft 2. 



t Cohn's Beitrdge, Band I, Heft 3. 



X Davaine had conducted a similar series of inoculations. 



