430 PROTECTIVE INOCULATION FOR BOVINE PLEURO-PNEUMONIA, 



that of vai'iola or small-pox, cause, when transferred to man, only 

 slight alterations, after which any attack of the virulent factors of 

 this disease will be frustrated. With regard to protective inocu- 

 lations of animals we may take as example that of anthrax. Here 

 the generally used cultures of micro-organisms are attenuated by 

 means of higher temperatures, so as to have lost their power of 

 infecting, while at the same time their morphological characters do 

 not differ from those of the virulent bacilli. Experience has 

 further shown that the inoculation-material prepared in the des- 

 cribed manner, must enter into a communication with those organs 

 or tissues which are the principal seat of the disease present, and 

 in which they have to call into existence symptoms, analogous 

 to those exhibited in the virulent form of the disease, but only 

 modified and often scarcely perceptible. The attenuated anthrax- 

 virus is transmitted through the subcutaneous connective tissue to 

 the blood, which is the seat of splenic fever. 



Nothing similar seems to take place with reference to pro- 

 tective inoculation for pleuro-pneumonia. In this case both the 

 kind of virus employed, and the part of the body where it is 

 applied, ai'e altogether contrary to those facts. There is, how- 

 ever, one cattle-disease, namely symptomatic anthrax ("quarter-ill," 

 " black-leg "), in which we find something analogous to pleuro- 

 pneumonia. "With regard to the foi'mer it has been proved beyond 

 doubt that, by means of direct injections of unweakened virus (e. g. 

 sap of diseased muscles) into the veins of healthy individuals, these 

 can be rendered immune, although the blood-system as such is not 

 the place where the contagium of the disease (the symptomatic 

 anthrax bacilli) settles, and carries on destruction. (The usual way, 

 however, in the practice of inoculation against this plague, is by 

 means of artificially weakened virus, applied subcutaneously). It 

 stands to reason that the same may possibly hold true with the 

 mode of protection against pleuro-pneumonia, for a liquid carrying 

 the infective matter in the shape of microscopic organisms, has, if 

 inoculated underneath the skin, every chance to be taken up by the 

 blood, and thus carried to the lungs and other organs. Bui in 



