THE SI LKNIC FEVElt. 37 



tagious bovine pleuropneumonia of Europe, and have witnessed them in outbreaks of 

 small-pox in sheep ; but in enzootic maladies, and especially in the various forms of anthrax, 

 it is not unfrequently found in post-mortems of animals from districts where such diseases 

 arise, that the healthiest and strongest have suffered or are suffering organic changes 

 which a special systemic vigor or constitutional resistance hides so long as the animals are 

 in life. 



Whether we study the malady as seen by me in Texas, or on Smoky Hill, in Kansas, 

 where a sudden shock to the system of a steer, on the occasion of its being stampeded, 

 developed symptoms and induced death; or look to the other animals, apparently fresh 

 and grazing, which indicated an abnormally high temperature of the body, it is evident 

 that a large herd, traveling from the region whence splenic fever is propagated, carries 

 not only the active cause of such propagation in the systems of animals composing it, but 

 the evidence of specific disease induced, which remains for an indefinite time latent and 

 unobserved. 



During the early part of our investigations we could not fail to be forcibly struck by 

 the apparently healthy condition of the vast herds of Texan steers which had scattered a 

 most deadly poison on the pastures of Illinois and Indiana; and even our dissections, limited 

 as they necessarily were, failed to elicit the truth. But the inspection of vast numbers 

 of Texan cattle in Kansas and in the Chicago slaughter-houses has proved that appear 

 ances may be very deceptive; and I consider that the abnormal weight of the spleen in 

 southern cattle, coupled, as such an indication is, with gastric redness and erosions, pale 

 blood, and the not unfrequent presence of bloody urine in the bladder, demonstrates that 

 splenic fever often, and indeed usually, occurs in a latent form among southern herds, 

 which communicate the disease; and none but a trained expert, thermometer and scalpel 

 in hand, can declare positively that any stock is in the enjoyment of perfect health. 



We are almost warranted in believing that the latent causes of splenic fever are 

 recognizable by the elevation of temperature; but this is a symptom of all fevers, and it 

 is only by studying this condition in relation to many other circumstances such as the 

 source whence stock is derived, the evidence of some unusual mortality, and the post 

 mortem indications of certain animals in a herd, concerning which there may be suspi 

 cions that it is possible to determine the presence of splenic fever in its occult form. 



The stages into which any case of splenic fever may be subdivided, and which are 

 readily recognizable in well-developed instances of the disease, are: 



I. The incubative stage. 

 II. The stage of invasion. 



III. The congestive or bleeding stage. 



IV. Termination. 



I. The incubative stage. The stage of incubation has not been satisfactorily deter 

 mined in individual cases; that is to say, it has been impossible, as yet, to obtain experi 

 mental facts which, as in the case of rinderpest and variola ovma, enable us to state 

 positively that, from the date of contamination of an animal by the poison, so many days 

 elapse before the manifestation of the disease, and that such period cannot be prolonged 

 beyond a definite and ascertained limit; nevertheless there are important data which 

 indicate that, from the period of arrival of a Texan herd on any distant or on any defined 

 pasture, five to six weeks elapse before the disease appears in the indigenous stock, grazing 



