BY DR OSCAR KATZ. 42T 



for a final decision, since opinions differ widely as to that point. 

 Yet we are warranted in saying a priori that, in a similar way as 

 it has been pronounced by von Pettenkofer for epidemic cholera, 

 the outbreak of an epidemic of pleuro-pneumonia must have been 

 preceded by an infection en masse. Infection of this description 

 could best be brought about by micro-oi'ganisms of the type of 

 facultative parasites (see above). In epidemics of anthrax and of 

 typhoid fever we cannot but trace such a course of things ; besides, 

 the statistic observations on the mode of spreading of cholera, 

 anthrax, and typhoid-fever, are altogether in concordance with the 

 results of laboratory experiments on the infectious nratter of these 

 diseases. On pleuro-pneumonia we fail to bring to bear such 

 powerful help ; for it is premature in this direction to draw 

 definite conclusions from the results of investigations by Peels and 

 Nolen, who have designated a certain micrococcus as the vera 

 causa of that bovine disease (^The Veterinarian, March 1887, pp. 

 143-157). In the interest of the matter itself their experiments 

 require expansion, and the results as yet obtained corroboration. 



Returning after this digression to onr subject proper we must 

 try to obtain a definite view of its essential characters. 



In its present shape protective inoculation for bovine pleuro- 

 pneumonia occupies a peculiar position among the other modern 

 inoculations or vaccinations. It is a matter sui generis. The 

 procedure is as follows : when the disease is stated to be present 

 in a herd, the vaccin is procured by killing one or more of the sick 

 individuals, and collecting the serum out of the diseased lungs, or 

 the pleural exudations. A definite portion of such liquids is then 

 ti'ansferred — the modtcs operandi differs — to the subcutaneous 

 connective tissue near the end of the tails of healthy, or we have 

 reason to add, apparently healthy individuals. This operation 

 gives rise to a localised swelling which is considered to be a repeti- 

 tion in a milder form of what takes place in lungs and pleurae in the 



