264 Seventeenth Annual Report of the 



course. Thus, the whole drove moving into a new district would 

 soon fail to leave behind it new centers of infection. 



It followed as a natural result that an infected herd, starting 

 for the West, from central Asia, must have lost its power of 

 transmitting infection in the first 20 days, or in the first 100 or 

 200 miles of travel. Before its arrival in even eastern Europe, 

 the drove must have consumed time enough to have represented 

 five or ten successive cases, each one following on the recovery of 

 its predecessor and passing through all the stages from inoculation 

 to complete recovery. 



It is not surprising, therefore, that in the mediaeval chronicles 

 we find more or less clear indications of the prevalence in Europe 

 of rinderpest, lung plague and tuberculosis, in the presence of a 

 remarkable silence as to foot and mouth disease. The earliest 

 unquestionable records of aphthous fever in Europe, accordingly, 

 lead back no further than two and a half centuries. 



As in the case of other contagious diseases of live stock in early 

 times, the immediate occasion of an invasion of central Europe 

 by aphthous fever has been usually found in a great European 

 war, and for a disease as rapidly infecting and as transient, this 

 war must have involved the far East. Then the necessity of supply 

 for both contending armies (Eastern and Western) imperatively 

 drew upon all lands within an available distance, and as the 

 nearer regions were depleted to supply the commissariat parks, 

 the further districts, next outside, were drawn upon in turn to 

 fill up the now scanty herds in the stock-raising area, and thus 

 the infection was spread from its primary sources into wider and 

 more distant fields. The continuance of the war and the move- 

 ments of the opposing armies, as a matter of course, drew the 

 infection further from its original home, until, in the case of 

 general hostilities, a whole continent was invaded and even a 

 second one was in the main overrun. 



This invasion by animal plagues, in the wake of invading armies, 

 has ever been one of the saddest chapters of great military enter- 

 prises. The historians have dwelt on the hecatombs of human 

 victims, the wasting of cities and fields by fire and sword, the de- 

 portation of captives, the ruin of great and important industries, 

 but they have been blind to, or have deliberately closed their eyes 



