56 THE LUNG PLAGUE OF CATTLE. 



In this way the trade is made quite profitable, for the cows are only 

 kept during the period of the fullest flow of milk, and when killed bring 

 a good sum for beef. Hence the remark "the cowfeeders did not know 

 how to make money until the disease came." Even the cows that are 

 happy enough to escape the plague are still disposed of for beef as soon as 

 the milk fails. None are kept on from year to year, none are sold to go 

 out into the country, and no calves are born in the dairies and raised for 

 stock. In these very exceptional conditions inoculation could scarcely 

 fail to succeed. The suspension of all cattle traffic, the slaughter of 

 the sick, and disinfection of the premises would of themselves have ac- 

 complished the same end independently of inoculation. This has been 

 done in all those countries which have really stamped out lung plague 

 alike in the Old World and the New. 



But if we reverse the conditions no snch uniformly good results could 

 be expected, and none susli have ever been obtained. Let the inocu- 

 lated cattle be sent from the infected city stables to the country, and 

 they would inevitably have carried the disease to many new centers. 

 Let calves be born and reared in these dairies, or be sent from them to 

 be reared elsewhere, and many of them would contract the disease them- 

 selves and convey it to others. Let inoculation be generally adopted 

 over an en tire, conn try, and it will be found impossible to prevent the 

 laying up of contagion in the buildings, fodder, &c., to develop the dis- 

 ease in the first susceptible animal that may be introduced. The first 

 new-born calf, or the first cow purchased, must be promptly inoculated 

 if we would protect her against the infected buildings and pastures. 



On hearing of inoculation, many conceive that it is the exact counter- 

 part of vaccination for small-pox, and that no more danger attaches to the 

 one operation than to the other. The difference, however, is fundamental. 

 In vaccination it is not the poison of smallpox that is used, but that of 

 cow-pox, a perfectly mild and harmless disease, which is utterly incapable 

 of propagating small-pox. In inoculation for lung plague, on the other 

 hand, it is the virus of genuine lung plague itself which is introduced 

 into the system, and the resulting disease, though it develops not in 

 the lungs, but (by selection) in the tail, is due to the propagation in the 

 last-named organ of the true virulent germs of the lung plague. As will 

 be seen by a reference above, to the record of Bouley and Yerheyen, 

 the inflammatory exudate in the tail contains the same virulent bacteria 

 as the diseased lung products, and, when inoculated on susceptible ani- 

 mals, produces the same series of local disease changes as if the pul- 

 monary product had been used. 



INOCULATED ANIMALS INFECTING. 



The advocates of inoculation mostly assume that the inoculated ani- 

 mal is not infecting. But such a claim, if it could be established, would 

 demolish their cherished theory of the protective influence of inoculation. 

 The virus they use for inoculation is the virus of genuine lung plague, and 

 if it fails to pullulate and grow, where inserted in the tail, it must equally 

 fail to fortify the system of that animal against a subsequent exposure 

 to this poison. If, however, as we fully concede, it is protecting, it can 

 only be because the germs of lung plague introduced into the system 

 have developed there and rendered the system proof against any sub- 

 sequent exposure to these germs. 



Before the introduction of vaccination for small-pox, some had prac- 



