September 19, 1884. 



SCIENCE, 



277 



in regard to their power. The first corre- 

 sponded to the ' mouse anthrax ' (that is, a cul- 

 ture from the eighteenth to the twenty-fourth 

 day) , while the second vaccination corre- 

 sponded to the ninth day. Six sheep were in- 

 oculated with these ; and out of these, one died 

 after inoculation with the malignant form. As 

 a result, it can be stated, that, after the most 

 careful protective vaccination, an unconditional 

 immunity against infective inoculation is not 

 reached in all cases. Koch thinks that Pas- 

 teur's perfect success must be due to the fact 

 that the malignant anthrax used by him was 

 not so virulent as he himself employed. 



The cause of the diminution of virulence is 

 regarded by Pasteur as due to the action of 

 oxygen; by Koch, on the other hand, as due 

 to the effects of temperature alone, even so 

 small an amount as a few tenths of a degree 

 C. causing a marked variation in the length of 

 time required to render the bacillus perfectly 

 harmless. Chauveau's experiments also point 

 in the same direction ; for while it took from 

 three to four weeks, at a temperature of 42.5" 

 C, to reach the desired result, it could be at- 

 tained in a few daj^s at 43° C, and in a few 

 hours at 47° C, while a few minutes sufficed 

 if a temperature of from 50° to 53° was used. 

 The lower, however, the temperature, the more 

 surely is the attenuation preserved in later cul- 

 tivations. When developed in the bodies of 

 animals for several successive generations, 

 Koch found that there was an occasional tend- 

 ency, on the one hand, for a weaker form to 

 become more powerful ; and, on the other, for 

 a stronger to become weaker. But, as a rule, 

 the degree was preserved unaltered, as in ar- 

 tificial cultures. 



The scientific fact that sheep could be ren- 

 dered safe against inoculated anthrax was con- 

 firmed by these experiments. The question 

 then arises, How do the vaccinated animals 

 conduct themselves against natural infection ? 

 As is well known, different kinds of animals 

 differ in this respect. Cattle, for example, are 

 very refractory to artificial inoculation, while 

 they are very often attacked from a natural 

 source. Pasteur regards the natural source of 

 infection as much less liable to produce the 

 disease than the artificial. His method of 

 placing a number of vaccinated animals in a 

 meadow, in which notorious cases had oc- 

 curred, is capable of such great errors that 

 it cannot be relied upon for scientific accu- 

 racy. 



What is the most common way in which 

 natural infection occurs? One method analo- 

 gous to inoculation is from the bites and stings 



of insects, who leave, at the same time, spores 

 of the bacillus, which may be attached to their 

 bodies. Another is by the inoculation of 

 scratches in the mouth, caused by sharp parti- 

 cles of fodder. 



Koch believes, however, that the intestine 

 itself is the common place of entrance for the 

 parasite, but only when in the condition of 

 spores. 



To show this, a portion of the spleen of an 

 animal who had died from anthrax was put 

 inside a small ball of potato, and placed on the 

 back part of the tongue of a sheep. In this 

 wa} T any clanger of wounding the mucous 

 membrane of the mouth was avoided. (Since 

 spores are never formed within the body, by 

 taking a portion of the organs, as above, it was 

 known that it was the bacilli alone that were 

 introduced.) Every experiment failed, even 

 after enormous doses, and thus proved that the 

 bacilli are destined in the stomach, and are 

 therefore not in a condition to produce intes- 

 tinal anthrax. When, however, the bacilli 

 were allowed to produce spores, and these were 

 given, every animal died. The examination af- 

 ter death showed that the spores had developed 

 in the intestinal tract, and the bacilli had in- 

 vaded the bod} T from these. It is therefore in 

 the highest degree probable that the introduc- 

 tion of spores with the food is the most common 

 source of natural infection. The amount would 

 never be so great at one time as was here used ; 

 but, if smaller doses were repeatedly given, the 

 picture of an ordinary epidemic could be nearly 

 reproduced. 



Cattle could not be obtained for experiment ; 

 but an examination made on a cow who had 

 died from natural infection showed similar le- 

 sions in the intestines to those found in the 

 sheep. 



Animals with a single stomach could not be 

 infected in this way. 



Finally the effects of protective inoculation 

 were tried. Ten sheep were taken : five of 

 these were vaccinated with material obtained 

 from Pasteur, of two different strengths ; and 

 five, according to Koch, with cultures of the 

 fifteenth, eleventh, ninth, and fifth day. They 

 were then fed with spores. As a result, two 

 of the first series died, but none of the sec- 

 ond. 



From these few yet unimpeachable experi- 

 ments, Koch concludes, that, for a certain num- 

 ber of animals, absolute immunity can be 

 obtained ; but he doubts whether a simple 

 vaccination, with only two different degrees of 

 attenuation of the virus, is sufficient to give 

 perfect protection. 



