DISTEMPER. 183 



conditions, such as exposure, debility, improper feeding, ill ventilated 

 kennels etc., are to be regarded no longer as exciting causes, and are to 

 be considered only in so far as they may increase susceptibility, favor ex- 

 tension, and possibly determine the severity of the disease. 



It is reasonable to suppose that inasmuch as the general system becomes 

 weakened by anti-hygienic influences.the power to resist contagion is les- 

 sened, the severity of disease is in a measure intensified, reaction and 

 repair are retarded, and mortality is thereby increased. 



The poison of distemper, as in other contagious diseases, can reproduce 

 itself under favorable conditions to an endless degree ; it retains its vitality 

 and power of infection for a long time outside of the organism which 

 produced it; it has no special stage of development to pass through on 

 the way from the affected organism to the one to be affected; but at the 

 time of infection it is essentially in the same condition as when given up 

 by the organism yielding it. That a simple attack of distemper success- 

 fully overcome, imparts an immunity from it for the remainder of life, is 

 a rule with only occasional exceptions. In explanation of the theory of 

 immunity bestowed on man by certain contagious diseases, it has been 

 suggested that something analagous to the ferment process takes place. 

 If yeast is placed in a fluid containing sugar, fermentation follows; when 

 all the sugar has been destroyed, and fermentation is complete, it cannot 

 be produced again by a further addition of sugar; the fluid responds no 

 longer to the action of the yeast. It is conjectural that during certain 

 contagious diseases there is a destruction or change in the body of some 

 chemical or constituent, the presence of which is a necessary condition for 

 the retention or development of the disease. It is not unreasonable to 

 suppose that in distemper something analogous takes place. 



The disease under consideration has been compared by some to the 

 typhoid fever of man; that it differs in its important symptoms, and 

 appearances as observed after death is true, but it seems that the greatest 

 disparity of all has been overlooked; typhoid fever belongs to the class 

 of miasmatic contagious diseases and is propagated in an essentiallj 

 different manner. 



Distemper can be conveyed by contact from a diseased animal to a 

 healthy one and produce the disease in him, while typhoid fever is not 

 contagious in the proper sense of the word, for it is never transmitted by 

 direct contact. On the profound difference in the mode of propagation 

 depends the essential difference in the two diseases. A far greater analogy 

 exists between typhus fever of man and distemper ; it belongs to the same 

 class of contagious diseases; the specific germ is evidently transmitted 

 and propagated in much the same manner. The incubation period, the 

 febrile stage, the duration, the self limitation, and many essential symp- 



