Epidemics. 157 



diseases in distinct classes of animals may be so closely allied 

 to each other that the lines of differentiation may culminate 

 in the line of their mutual substitution, with the reduction 

 o^ their mutual activities in the order of propagation ; as 

 in cow-pox, for small-pox, virus, by transplanting or exchange 

 becoming nil for infection from the side of cattle to man, 

 but analogous in differentiation or change in the nutritive 

 functions of cell life, whereby resistance to repetition of the 

 disease is obtained as completely in one form of the disease 

 as the other, or as perfectly by the invader as the aboriginal, 

 which demonstrates their proximity of parentage, or in 

 familiar language, consanguinity. 



The same author, Dr. Bascome, gives another illustration 

 of the approximation in diseases of cattle to that of man, 

 when it is present in the form of pestilence. He quotes from 

 a Roman author, whose name is not given, but whose views 

 are fully expressed in one short clause* : " Pestilentia quae 

 priore anno ingruerat in boves, eo veteret in hominum 

 morbos." However similar or dissimilar pestilence in cattle 

 and man might be within the short space of one year, no 

 doubt can exist, from the clause quoted, that the Roman 

 writer considered that it was the same pestilence which 

 was destructive to man that was the year previous destruc- 

 tive to horned cattle. 



The general sentiment which is here conveyed by an 

 ancient writer is fully substantiated by a long succession of 

 epidemic periods since he wrote namely, that epidemic 

 disease in the bovine species has very frequently been 

 preceded or followed by epidemic disease in man. In our 

 own days this has been exemplified in the pleuro-pneu- 

 monia of cattle of 1846, preceding and following the 

 cholera of 1849 and 1853, but since 1855 it has been 

 gradually declining, but is more common in man of 



* Dr. Bascome on " Epidemics," page n, 1851. 



