CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 37 



tliem to the West. It was absolutely iiupossible to fiud auy satisfac- 

 tory manner b}' wbicli a foreign coutagiou could bave been introduced. 



This important indication seems to bave been greatly neglected iu 

 deciding ni)()n the nature of the disease in Kansas. It was said if this 

 is foot-and-mouth disease we must acknowledge that we have it, whether 

 we can trace its introduction or not. Plausible as this reasoning may 

 seeni we must admit that it is not always an easy matter to diagnose a 

 disease ott'-hand from its superficial characters. And in the diagnosis' 

 of contagious diseases we must remember that the symptoms are but 

 the expression of the effects of the virus, and that these symptoms 

 may be simulated more or less closely by other agencies acting upon 

 the animal economy. 



The history of the origin of any disease believed to be contagious is, 

 then, a most important part of the evidence to be taken into considera- 

 tion before a diagnosis is reached. We may take contagious pleuro- 

 pneumonia for example. Many cases of this disease resemble so closely 

 spontaneous inflamnuitions of the resi)iratory organs iu cattle that it is 

 absolutely necessarj' before a diagnosis can be reached to inquire if the 

 contagious pleuropneumonia has been introduced or if the malady occur- 

 red spontaneously. The same principle holds good to a greater or less 

 extent with other diseases, and it may be safelj' asserted that when the 

 history does not receive proper consideration many mistakes will be 

 made that otherwise might be avoided. 



Confaf/iovsness. — Thevirus of foot-and-mouth disease is one of the most 

 active contagions know^n. The period which elapses between exposure 

 and the appearance of the first symptoms of the disease is, as a rule, 

 but two or three days; a very large proportion of exposed animals be- 

 come diseased, and the plague spreads rapidly from farm to farm. As 

 a result of these characters, within a week after the introduction of 

 foot and-mouth disease into a herd nearly every animal in that herd 

 shows unmistakable evidences of having contracted it. A very snuiU 

 proportion of the animals may resist the contagion, but this proportion 

 is much less than with most other contagious diseases, and is so small 

 that it does not affect the rule just mentioned. 



The disease at Neosho Falls showed very different characters from 

 this. Goodrich's herd suffered in the largest proportion. Go out of 90, 

 or 68 per cent., being more or less affected. The first case here 

 occurred January 10, and no others until February- 15, or more than 

 a month later. After this new case.s continued to develop for two or 

 three weeks. But in a lot adjoining that in which the sick cattle 

 Mere placed there were 20 calves, which remained entirely free from 

 disease. The isolation of these calves was not sutlicient to iiold foot- 

 and-mouth disease in check for a single day; it was even said that the 

 sick cattle had been driven through the calf lot to water, and that some 

 of the smaller ones, when attacked, were placed with the calves. 



At Keith's 74 out of a total of 118, or 03 per cent., were affected. 



