272 Seventeenth Annual Report of the 



taken. In two weeks all had passed through the disease, and when 

 later the spring calves were born (February and March), these 

 susceptible offspring never once, in my extended experience, con- 

 tracted foot and mouth disease. 



A similar demonstration on a larger scale was made in 1870, 

 during the great epizootic that swept over Canada, New York and 

 New England. This reached New York almost at the same season 

 as did that of 1908, when the stock were just about to go into 

 winter quarters. In the absence of any official quarantine or dis- 

 infection, each herd, closely shut up in stables and yards, passed 

 rapidly through the attack and recovered, and in this case when 

 the susceptible spring calves were born, not one of them became 

 infected, and the epizootic and its infection were alike definitely 

 ended. Here we had not 370 cattle as in the Bernese Oberland, 

 but a million or more, and if the virus had remained in the systems 

 of the recovered animals it is simply incredible that the great 

 crops of spring calves could have escaped as they actually did. 

 Here, too, we had a winter which differed from that of England 

 in being at least as severe as that of the Bernese hills, yet neither 

 in the uplands nor in the valleys did a remnant of infection sur- 

 vive to start a fresh outbreak. But in a country like Switzerland, 

 where aphthous fever is almost a constant guest, the possibility of 

 infection from outside, unsuspected sources is an ever-present 

 peril, and it becomes a temptation to attribute to virus preserved 

 in the system of a recovered animal a new outbreak which had 

 another and more substantial foundation. Do°s and other do- 

 mestic animals, rats, mice, vermin of various kinds, birds, infected 

 fodder, human beings, summer flies and many other possible chan- 

 nels of accidental infection must be thoroughly considered and 

 excluded before we assume the much more improbable survival of 

 infection in the recovered. The very recovery shows that the 

 phagocytes and defensive liquids of the body have done their work 

 and disposed of the invading microbes. Otherwise, the malady 

 would have continued, and if equal to the destroying of the 

 microbe in the full plentitude of its power, in the height of the 

 disease, much more would they triumph over the one which has 

 been already overcome and put to rout in a recovering system. 



The theorv of the lenarthv survival of the virus in the svstem 



