I. AGRICULTURE AND RURAL ECONOMY. 333 



of rinderpest is transmitted, in part, by direct contact with 

 diseased animals, and partly by the emanations from living 

 and dead animals, affected, although not to any great dis- 

 tance at any one time. 4. In the south of Russia rinderpest 

 is, comparatively, less contagious and dangerous than in oth- 

 er portions of the empire. 5. In summer and winter the rin- 

 derpest is generally less violent than in spring and autumn. 

 Autumn is the most unfavorable time for inoculation of rin- 

 derpest, the most favorable time being that in which a mod- 

 erate temperature predominates. 6. All races of cattle are 

 not equally sensitive to contagion of rinderpest. Those less 

 liable are the Kirgus and Kalmuck races, belonging to the 

 steppes. 7. The alleged mitigation and weakening of the vi- 

 rus by repeated inoculation, and in the succeeding genera- 

 tions, does not prove to be substantially true, according to 

 the experiments of Robichew, as even in the fifteenth gener- 

 ation it did not seem to have lost its activity. Professor Jes- 

 sen considers, however, that the question of the weakening 

 of the virus can not be regarded as closed until a special se- 

 ries of experiments has been instituted, in which the conta- 

 gion has been inoculated from the first generation, on grad- 

 ually, to complete inactivity. 8. It has not been determined, 

 positively, by the experiments how long the pest contagion 

 maintains its aggressive activity. In many cases the virus 

 loses its infecting power after the course of a few days; in 

 others it remains many months. It must, nevertheless, not 

 be overlooked that the aggressive power of the contagion 

 may be dependent upon its preservation or other influences. 

 Single cases of inactivity of the virus may be explained un- 

 der the supposition that this has lost its activity in conse- 

 quence of the milder nature of the epizootic, or the animals 

 inoculated with the virus did not become ill, or only in a 

 slight degree, on account of their want of sensitiveness to the 

 contagion, or because they had already experienced the natu- 

 ral disease. 9. In regard to the action of fresh and old virus, 

 experiments have shown that the former generally produces 

 more, and the latter less violent sickness, and, in many cases, 

 the latter is even inactive. 10. Animals which become vio- 

 lently ill under inoculation, and show the characteristic in- 

 dications of rinderpest, are not sensitive to further infection. 

 Such animals, however, as are but slightly ill after infection 



