14 Veterinary Medicine. 



The terms enthetic, zymotic, and contagious best express 

 modern views of the nature of these maladies. The term infec- 

 tious when used to express a gaseous or otherwise intangible 

 (unorganized) body, or influence transmitted through the air, 

 necessarily excludes the particulate, living, self-propagating 

 germ upon which the transmissibility of the disease depends. A 

 chemical, electrical, or other body or influence generated outside 

 the animal body, cannot well be ' conceived of as reproducing 

 itself within the animal body, but must act like any other 

 ectogenous poison, according to the size of the dose and the 

 frequency of its exhibition. This might create an enzootic 

 disease, but would lack all the qualities of a contagious affection 

 since it could not spread from a victim when taken elsewhere 

 and turned among animals which would prove equally suscepti- 

 ble if placed within the infecting area. Suppose on the other 

 hand we apply the term infectious to diseases in which the levity 

 of the particulate living germ allows of its being inhaled into the 

 body of the susceptible animal, the case becomes one of simple 

 mediate contagion, the air acting as the intermediate bearer. 



The term zymotic conveys a clear idea of the method of in- 

 crease of the disease germ in the body by the ordinary process of 

 generation. The old doctrine of fermentation by a continuous 

 change, due to contact with dead fermenting matter, as an inflam- 

 mable body continues to burn by contact with the incandescent por- 

 tion, has been definitely disproved by the investigations of Pasteur 

 and others, and today we must recognize that every fermentation 

 is the result of the propagation and vital activity of living or- 

 ganisms. This does not ignore the fact that the chemical prod- 

 ucts or enzymes which are constructed by the vital activity of the 

 microbes, will dissolve or transform organic matter, but in the 

 absence of the microbe no such enzyme can reproduce nor mul- 

 tiply itself and its action must therefore be exactly limited by its 

 amount. The living germ itself is therefore the one effective 

 factor, by which the contagious disease may be maintained and 

 propagated. In its turn the living germ can only come from a 

 pre-existing living germ. To the scientist of today the doctrine 

 of spontaneous generation is a thing of the past and the aphorism 

 omnis ovum ex ovo is dominant. The argument drawn from the 

 saccharizing of starch in the germinating seed by the operation of 



