212 



SCIENCE. 



[Vol. II., No. 20. 



pending the choice of time bj' the British 

 association for their Montreal meeting. A 

 preference, however, has been inclicated for the 

 ■week beginning Sept. 3, — a date earlier than 

 usual, but welcome to all who know how warm 

 Philadelphia can be in August. 



w. c. w. 



RELIABILITY OF THE EVIDENCE OB- 

 TAINED IN THE STUDY OF CONTAGIA. 



There is certainly a disposition, among some 

 of our scientific men, to doubt the possibility 

 of making direct and satisfactory demonstra- 

 tions of the r(5,'e played by the schizophytes, 

 or microbia, in the production of disease, and 

 that which they may be compelled to take in 

 its prevention. Kecent publications by ac- 

 cepted authorities have tended rather to con- 

 firm these doubts than to remove them, and 

 we are frequently asked if our results are not 

 founded on probabilities rather than on defi- 

 nite and conclusive facts. While this uncer- 

 tainty is still felt, it is well to occasionally 

 review the connection between the facts estab- 

 lished and the conclusions drawn from them. 



Though the schizophytes are the smallest of 

 living organisms, that is not an insurmountable 

 obstacle to their careful study, as is proved by 

 the well-known investigations of the Bacillus 

 anthracis by Koch. His demonstration that 

 this exists in two forms (a vegetating filament 

 and a spore) , and that the latter survives un- 

 favorable conditions which destroj- the former, 

 enabled him to trace a connection between the 

 activity of the virus and the life of the para- 

 site, which other investigators had failed to 

 establish. Thus, the blood of anthrax vic- 

 tims, which contained only Bacillus rods, lost 

 its power to reproduce the disease after a few 

 davs' putrefaction ; while that which contained 

 spores remained virulent an indefinite time. 

 A certain degree of cold, and also an insuffi- 

 cient supply of oxygen, prevent the formation 

 of spores ; and, the filaments being short-lived, 

 the organism loses its vitality in a few days 

 under such conditions. If spores had formed 

 before the liquid was exposed to these con- 

 ditions, however, they were unaffected, and 

 were capable of germination after weeks or 

 months. Again : if a virulent liquid was large- 

 Ij- diluted, the filaments were deslroj'ed, but the 

 spores survived. In all these cases the activ- 

 ity of the virus disappeared with the death of 

 the organism, and was retained whenever the 

 formation of spores had enabled this to resist 

 the unfavorable conditions. 



Here was a proof of the pathogenic charac- 

 ter of the schizophyte mucli more satisfactory 

 than the mere demonstration of its presence iu 

 all cases of the disease, or the additional evi- 

 dence that it might be passed through a certain 

 number of cultivation-flasks ; the liquid in the 

 last being as virulent as in the first. 



Since Koch's paper was published, Pasteur 

 has added observations of an equally convin- 

 cing character. The liquid part of the virus 

 may be freed from the organism either bj' 

 filtering through plaster or by decanting after 

 it has stood in a constant temperature for a 

 few days to allow the germs to gravitate to the 

 bottom of the flask. In either case the liquid 

 is harmless, and the separated germs still pro- 

 duce the disease. Again: compressed oxygen 

 destroys the filaments, but does not affect the 

 spores ; and a virus containing only the former 

 loses its activity when treated with this agent, 

 while one in which spores have formed retains 

 its virulence. 



We are able to say, therefore, that, in the 

 disease known hy the French as charbon and 

 b}' the English as anthrax, no liquid is virulent 

 unless it contains the living Bacillus anthracis, 

 and that the death of this organism always 

 coincides with the destruction of the virulence. 



This demonstration of the pathogenic action 

 of the Bacillus cannot but be regarded as equal- 

 ly satisfactory with what is obtained by inves- 

 tigations in other departments of biological 

 science. If the observations of these gentle- 

 men are accurate, and they have been con- 

 firmed too often to be doubted, then there is 

 no escaping the conclusion that the Bacillus 

 anthracis is the essential and only cause of 

 anthrax. 



It is not to be denied, however, that the 

 size of the parasite in anthrax, and the fact 

 of its existence under two forms having such 

 unequal resistance to unfavorable conditions, 

 were characters which greatl3' facilitated the 

 demonstration of its pathogenic relation to 

 the disease. Is it possible to obtain equallj- 

 satisfactory evidence in regard to the smallest 

 of the schizophytes, and one which only exists 

 iu the vegetating condition ? 



The micrococcus of chicken-cholera is of 

 tills kind, and it is consequently very inter- 

 esting to see just what progress we have made 

 in demonstrating its identity with the virulent 

 principle. We know from Pasteur's investi- 

 gations that it is always present in this dis- 

 ease ; that it may be cultivated, and passed 

 from flask to flask for man}' times, without 

 losing its virulence. The filtered liquid loses 

 its activity ; that from which the germs are 



