44 THE CANADL\N NATURALIST. [Vol. vii. 



and vegetable matters. These entering the blood in the process 

 of respiration, poison it, and produce such diseases as the one 

 under consideration. The most careful chemical analyses fail to 

 detect them, and we recognize them only in their effects upon 

 the blood and system in general. 



Like all poisons, those producing zymotic diseases appear to 

 be subject to certain general laws, the most important of which 

 are, according to Dr. Aitken, (1) That they have all certain 

 definite and specific actions ; (2) That they all lie latent in the 

 system, a certain but varying period of time before their actions 

 are set up ; and (3) That the phenomena resulting from their 

 action vary in some degree according to the dose and the recep. 

 tivity of the patient. 



Zymotic poisons have been divided into three classes, viz., 

 1. Paludal malarious poisons; 2. Animal malarious poisons; 

 3. Specific disease poisons. The first do not exert their influence 

 upon domestic animals to the same extent as upon man. They 

 result from the decomposition of vegetable substances, and may 

 be carried by the wind to considerable distances, giving rise to 

 agues, rheumatic fevers, and other diseases. The second arise 

 from the decomposition of various animal substances. The 

 winter season, when the dwellings of man and beast are too often 

 overcrowded and ill ventilated, is favourable to their develop- 

 ment. The blood becomes charged with them, and they exert a 

 depressing influence upon the system. The third or "specific 

 disease poisons," are derived from the bodies of animals suffering 

 from the disease ; for the body once contaminated by the poison^ 

 is capable of generating it and spreading the disease to others. 



Mr. McEachran here gives several extracts from Dr. Beale's 

 book on "Disease Germs," relating more especially to the spread 

 of infectious diseases ; but we must omit them and pass on to 

 such points as the symptoms and treatment of Epizootic In- 

 fluenza, using Mr. McEachran's own words as far as possible. 



As is generally known the present epizootic made its appear- 

 ance in Toronto in the beginning of October, and there soon 

 spread to such an extent as to completely arrest all business de- 

 pending upon horses — scarcely a horse escaping. From Toronto 

 it gradually extended in an easterly direction, until, on the 8th 

 of October, one case was detected in this city. On the morning 

 of that day my attention was directed to a peculiar deep cough 

 affecting a mare belonging to a gentleman in this city. On ex- 



