BY DR. OSCAR KATZ. 429 



siibject to considerable fluctuations, thus rendering the question of 

 making a correct diagnosis a matter of considerable embarrassment 

 In view of such facts, the above factor in connection with inocu- 

 lation for " pleuro " is pre-eminent ; it must be looked upon 

 as a very strong objection to the measure in its pi-esent state, 

 unless experiments can show beyond every doubt that immunity 

 through inoculation is also bestowed UDon such animals as are 

 already infected. Otherwise the manipulation, instead of pre- 

 venting the disease from spreading, would tend to preserve and 

 propagate it, by allowing vaccinated but previously affected indivi- 

 duals to pass as being safe. It is true that in the most modern 

 protective inoculation, namely Pasteur's treatment of hydrophobia, 

 we find an instance which seems to correspond to a postulate of 

 the above kind. Pasteur applies his method not until his patients 

 have been bitten by a rabid animal, and, consequently are already 

 impregnated with the deadly virus. For the present, however, it is 

 advisable to view Avith some reserve Pasteur's results so far as 

 rabies is concerned. 



Another point that calls for our attention is this. How is it that 

 in pleuro-pneumonia the material to be inoculated has the shape of 

 a virus, taken directly from the diseased oi-gans, and in this condi- 

 tion applied to the subcutaneous cellular tissue of the tail, that is to 

 say, to spots which have nothing to do with the chief seats of the 

 malady 1 With one exception (see below), there is no analogy to 

 this extraordinary case in the other protective inoculations 

 which have been made known. Here vaccins are used which 

 although morphologically very similar to, or, as a rule, quite the 

 same as the virulent agents, are weakened, partly naturally, 

 partly artificially, to such a degree that they are no longer able to 

 kill the individual species for which they are intended. The 

 vaccine-lymph for small-pox vaccination represents the virulent 

 material of vaccine or cow-pox, but such a material or, if you like, 

 bacterial life and its pi'oducts, although extraordinarily alike to 



