98 Veterinary Medicine. 



crobes, have in the great majority of cases led to little or no 

 evil result (Gamgee, Mayo, Dinwiddie, etc.) and there is a 

 strong tendency to discredit the pathogenic action of these 

 agents in reported outbreaks. The safer conclusion perhaps 

 would be, to recognize the fact that they are not equally patho- 

 genic under all conditions of their growth and administration. 

 The oft-recurring epizootics of brain disease in connection with 

 wide spread spoiling of the fodders in remote and recent times, 

 probably imply that cryptogams or microbes and their products, 

 plus some condition not yet fully understood are efficient con- 

 current factors. If we can discover this as yet unknown factor 

 and demonstrate that it operates with equal power in the ab- 

 sence of the cryptogams and ferments, as in their presence, it 

 will be logical to pronounce these latter as nonpathogenic under 

 all circumstances. Until then cryptogams and bacteria must be 

 held as probable factors. 



A continuance of high temperature is an undoubted factor 

 and becomes more potent, if conjoined with a close, damp, ill- 

 aired stable. 



Violent exertion especially in hot weather produces active 

 congestion of the brain and occasionally merges into meningo- 

 encephalitis. If the animal has been for sometime confined to 

 the stable on rich aliment' the condition is aggravated. 



Railroad travel is another recognized cause. 



Any considerable change of the conditions of life may 

 operate in the same way. A sale and transport to a distance 

 with change of feed, water, work, stabling and even of climate 

 is at times a potent factor. Prietsch has seen a horse attacked 

 three times in a single year, and on each occasion after a change 

 of ownership and locality. Trasbot quotes an Algerian veteri- 

 narian to the effect that many of the Percheron horses imported 

 into the Mitidja are attacked by encephalo-meningitis during 

 the extreme heats of summer. 



A careful observation of cases will however show that in the 

 majority of cases an attack comes not from one individual 

 factor alone but from a concurrence of several operating together. 



Other cases are caused by embolisms and infections from 

 diseases localized in other parts of the body. Thus we have 

 cerebral abscess in pyaemia, strangles and omphalitis, and cerebral 



