THE ETIOLOGY OF RABIES. 
163 
I 
'condition or circumstance which.can bring about or predispose to 
the development of the disease, excepting only the contagious 
principle as transmitted from rabid animals. The origin of the 
malady in the canine and feline species is, in many instances, in¬ 
volved in the greatest obscurity, and, being unable to account for 
these cases upon any other supposition, many observers have 
believed in the occasional spontaneous origin of the disease. 
Fleming, the ablest of the recent English writers on this subject, 
says: “And rabies, we feel we are justified in asserting, must 
ilso be included in the list of diseases with glanders, anthrax, 
yphus in pigs, and the distemper in dogs, which, generated under 
certain favorable conditions, during their course develop a virus 
; hat, like a ferment, acts as a leaven in producing morbid and 
iharacteristic changes when it obtains admission to the previously 
lealthy body, and there are few nowadays who are not convinced 
phatit will occasionally appear in a spontaneous manner and with¬ 
out any exciting cause.” 
The most potent arguments which have been brought forward 
is proving the spontaneous development of rabies are : 1. The 
ippearance of the disease in an epizootic form in countries where 
t has been previously unknown, and where its appearance could 
iot be traced back to any foreign source. The epidemic of the 
lisease in Peru, in 1803, may be cited as an instance of this kind, 
h It is urged that the appearance of the disease in an epizootic 
orm in some countries at rare intervals can also only be explain¬ 
ed in a satisfactory manner on this hypothesis. It has been 
'bserved, not infrequently, that, in certain countries which have 
>een free from the disease for long periods of time, suddenly it 
ppears in almost an epidemic form, and, after a short time, 
>ecomes again apparently extinct. Dr. Roucher, as quoted by 
Fleming, refers to the appearance of the malady in Algeria as 
onfirmatory to some extent of its spontaneous origin. The 
aarked intermittence in its manifestation at different geographical 
enters; the multiplicity of cases at certain epochs of very short 
uration, contrasting strikingly with their rarity at other times; 
!ie intervals between the outbreaks, which are longer than the 
eriod of incubation of the virus; the small number of cases as 
