DISEASES OF SWIXE AND OTHER ANIMALS. 165 



sale of tliem by owners, or the killinfj of all animals that have been ex- 

 posed to the disease, mnst be enacted as will effectually put a stop to 

 the spread of it over this country. 



I am, very respectfully, your obedient servant, 



EEUBEX F. DYER, M. D. 

 Ottawa, III., October 1, 1878. 



EEPOET OF DE. ALBAN S. PAYI^. 



Hon. Wm. G. Le Due, 



Commissioner of Agriculture : 



Sir: My description of this disease (so-called hojj-cholera) will be con- 

 fined to its history as it invaded that beautiful section of country lying 

 between tlie Blue Eidge and tlie Catoctin chain of mountains, in Vir- 

 ginia, diuing" the summers of 18G9-'77-'78. 



GENERAL CONSIDER ATIONS ON CONTAGION. 



Before speaking of the endemic and epidemic disease under considera- 

 tion, generally known as hog-cholera, although a palpable misnomer, I 

 will offer a few remarks upon the subject of contagion. This is always 

 a question of paramount importance, not only to the investigator of dis- 

 eases, but to the people at large. One great difficulty in arriving at a 

 definite conclusion as to the contagion or non-contagion of a disease, I 

 am persuaded, arises from the too great latitude given to the definition 

 of the word contagion by the older and more systematic writers. In the 

 sense in which this term is used at the present time it strikes my 

 mind as being too vague and indefinite. The same objection may 

 be urged against the term infection. For if you mean to signify 

 by the term contagion a disease that transmits disease from one 

 subject to another by du^ect contact, without the assistance of any 

 susceptibility or predisposing cause on the part of the patient, 

 I should then contend that very few epidemic or endemic diseases were 

 so, strictly speaking. But if you mean by contagion to signify a disease 

 from which exhalations or emanations may arise during its progress, 

 capable of exciting a similar disease in those exposed to the intiueuce of 

 the noxious exhalations, or rather deoxygenizing emanations, then I 

 will say that most of these epidemic and endemic diseases to which man 

 and the domesticated animals are equally liable are more or less conta- 

 gious. For here you have an exciting cause furnished by a foul deoxy- 

 genized atmosphere and a predisposing cause furnished by a weakened, 

 impoverished system from improper food, bad water, or from the want 

 of proper protection from inclement weather, or fi-om sudden climatic 

 alternations, causes sufficient of themselves, under certain circumstances 

 (which we call epidemic intluences), to produce disease in man or domes- 

 tic animals. Infection is as unfortunate and indefinite a term; nor 

 are the terms "specific" contagion and "contingent" contagion, as 

 defined at the present day, by any means explicit. In my humbly oi)in- 

 ion fevers are a unit, varied in their character by surrounding cu'cimi- 

 stances ; that is, in a temperate climate a remittent bilious fever becomes 

 yellow fever in a hot climate when the temperature of the atmosphere is 

 at its acme of power. The theories of ozone, " disease germs," micro- 

 cocci, ^'c, are very plausible in theory, but they have yet to be ijroveu. 



