266 Inoculation for Pleuro- Pneumonia in Cattle. 



second action of the morbific matter. In small-pox and other 

 diseases of the class, we trace this immunity to the production 

 of the malady by artificial means, and this production to an 

 augmentation of its special virus within the organism. 



The protection afforded by vaccination to an individual against 

 small-pox stands upon a foundation equally secure with that of 

 inoculation. " The vaccine disease " is in reality the small-pox 

 of the cow. By the process which has been named vaccination 

 the smail-pox of the cow is transmitted to man, and fortunately 

 with incalculable benefit, because, while the disease possesses the 

 same nature^ it wants the malignancy of human small-pox. 



The experiments we have herein recorded prove that some of 

 the animals were susceptible to the action of the serous exuda- 

 tions of the diseased lung, not only a second hut a third time., or 

 oftener. These cases are too numerous to be viewed simply as 

 exceptions, for in our first experiments, out of seven selected 

 animals, selected because of the success of the inoculation, no less 

 than four were immediately acted on by a second inoculation. 

 Nor do we stand alone in proving these facts ; the Belgian 

 Commissioners, as v/e have previously remarked, state " that 

 the phenomena succeeding inoculation may be produced several 

 times in the same animal ;" and they add, what is of equal im- 

 portance, " which may or may not have been attacked with 

 exudative Pleuro-pneumonia." 



We admit that the period of immunity afforded by inoculation 

 as a general principle does vary in different diseases, and also 

 in the same disease in different animals. What, we ask, is the 

 proof of this immunity being lost? Why, the susceptibility of 

 the animal to a /-e-inoculation. If this should fail, the animal 

 was secure ; if succeed, the animal was unprotected. Among 

 the cows we have alluded to were some which had been inocu- 

 lated only three weeks before, and in others the effects of the 

 first operation were still manifest at the time of the successful re- 

 inoculation. In our experiments also, when we succeeded in 

 producing effects which would give perfect satisfaction to the 

 advocates of the system, by inoculation with the serous fluid, we 

 have taken the product of this inoculation and used it forthwith 

 on the selfsame animal as well as on others, and obtained results 

 equally as great as from the original inoculation. How could 

 these things be explained were we dealing with a specific virus ? 



We have called this product sero-purulent fluid, and so in 

 reality it is when first exuded from the wound, but it presently 

 becomes altogether and entirely pus. Our experience therefore 

 confirms that which we had anticipated with regard to these in- 

 oculations hy removes, namely, that the effect would be both more 

 certain and speedy, because pus was the material employed. 



