250 CONTAGIOUS DISEASES OF DOMESTICATED ANIMALS. 



7. In higher altitudes, buch as in Colorado for instance, the south- 

 ern cattle fever, although sometimes appearing after an infection of the 

 grounds by Southern cattle, is much less malignant than in the lower 

 countries farther east, antl comparatively seldom proves fatal, a fact 

 which may find its explanation that in a higher altitude the atmosphere 

 is thinner and dryer, and less charged with organic substances ; besides, 

 the temperature, on an average, is lower. All this is less favorable to 

 a. deca^' of vegetable substances and a propagation of bacteritic growth 

 than the warmer climate and the more dense and moist atmosphere of 

 a lower country. The dead or dried grasses of the Colorado plains, 

 under the influence of the dry air, and often prevailing dry winds, are 

 g,Tound to dust, and thus disappear before any decay sets in. 



8. The morbidly attected tissues of animals affected with or killed by 

 the southern cattle fever, even if examined at once, invariably contain 

 bacteria* of the micrococcus and bacillus kind, and it appears to be very 

 probable, particularly in the light of recent research in regard to infec- 

 tious diseases and their causes, that at least one of these two kinds of 

 bacteria bears some causal connection to the morbid process. My own 

 observations, examinations, experiments, and a careful consideration 

 of undeniable facts, point toward the bacilli, and not to the micrococci- 

 My reasons I shall take the liberty to state further on. 



9. If all the facts known in regard to the communication of southern 

 ■cattle fever to Northern cattle by means of trails, grazing grounds, past- 

 ures, water-holes, «!ycc., are duly considered as they present themselves^ 

 there can hardly remain any doubt that the infection of the trails, past- 

 ures, &c., must be etfected by means of the saliva or slaver of the south, 

 ern cattle. In proof of this assertion I may be allowed to state a few 

 facts bearing on this point, and also to briefly dwell upon other theories 

 now and then advanced. First, as to the latter. One theory charges 

 the infection to a deposit of the urine of the Southern cattle. If it were 

 tlie urine that causes the infection only those comparatively small and 

 far apart spots in which the urine of the Southern cattle is deposited 

 would be able to communicate the disease to Northern cattle, for it has 

 been established beyond a doubt that the infectious principle is not car- 

 ried through the air or disseminated by winds, and that even a wire 

 fence separating a pasture occupied by Northern cattle from a trail or 

 pasture of Texas cattle {cf. my last report) is ample protection. Besides, 

 cattle are not apt to graze where another animal has urinated ; and as 

 the urine is sodn absorbed by the ground or evaporated it could never 

 be explained how it can be possible that the infectiousness of a pasture 

 or^trail increases in intensity, at least for several weeks after the South- 

 ern cattle have left it. If the urine constituted the vehicle of the infec- 

 tious principle, the wholesale infection of every Northern herd of cattle 

 that passes over and grazes on a trail of the Southerners, or feeds on 



* The word "bacteria," unless otherwise stated, is used as a jcpn^ric term, because 

 better understood by the avcrago reader thau Scliizophytos or Schizomycetes. 



