122 Veterinary Medicine. 



Accessory Causes. The recognition of the one essential cause 

 in the microbian invasion, need not exclude as accessory factors 

 the many unwholesome conditions which have long been 

 recognized as contributing to the severity of epizootics. As the 

 seed requires the rich field, the rain and sunshine to bring it to 

 an abundant harvest so the microbe of equine influenza flourishes 

 best where the conditions are most favorable and the antagonisms 

 least. 



The chill which comes from a sudden extreme fall of tempera- 

 ture, or the standing in a cold draught when wet or perspiring, 

 lays the system open to this as to other microbian invasions. 



The electric tension preceding a thunderstorm, to which many of 

 the lower animals are excessively susceptible equally prepares the 

 system to succumb to the germs. It may here be noted that Sep- 

 tember 1872, the last days of which witnessed the start of the 

 great epizootic, had no less than eleven thunderstorms, while in 

 September of the previous year there were but two in the vicinity 

 of Toronto. It is just possible that the great and frequent 

 electric tension, lowered the animal vitality, allowing a violent 

 invasion by the hitherto slumbering germ, and gave to the latter 

 that encreased potency which sent it forth on that year of almost 

 unparalled epizootic record. 



The high barometer and low dew point similarly affect the ani- 

 mal economy and encrease receptivity to disease. Rain fell at 

 Toronto 16 days in September 1872 and but 8 days in September 

 1871. 



Impurities in the air whether originating in volcanic eruptions, 

 telluric emanations, close, filthy overcrowded buildings or com- 

 partments or large collections of decomposing organic matter, 

 impair the animal vigor and lay the system open to a more 

 violent attack. For this among other reasons epizootics of 

 equine influenza are nearly always more deadly in the closely 

 packed city stables than in the pure country air. 



Overwork and poor irregular feeding and watering pave the 

 way for debility, prostration and severe invasion. 



Sudden vicissitudes of temperature, which are so common in 

 spring and autumn, associated as they are with the shedding and 

 growth of the coat, materially encrease susceptibility and .sometimes 

 determine an encreased severity in the attack. 



