SPLENIC OR PERIODIC FEVER OF CATTLE. 95 



Whether we study the malady as seen by me in Texas, or on Saioky 

 Hill, in Kansas, where a sudden shook 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 indi- 

 cated 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 iudeliuite 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 failed, limited as they 

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

 of Texan cattle in Kansas, and in the Chicago slaughter-houses, have 

 proved that appearances may be very deceptive ; and I consider that 

 the abnormal weights of the spleen of southeru 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, demonstrate that 

 splenic fever often, and indeed nsually, occurs in a latent form among 

 southern herds, which communicate the disease : and none but a framed 

 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 rela- 

 tion 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 

 suspicions, 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, 

 but 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 incuhative stage. — The stage of incubation has not been satis- 

 factorily determined in individual cases ; that is to say, it has been im- 

 possible, as yet, to obtain experimental facts which, as in the case of rin- 

 derpest an<l variola ovina, enable us to state positively that, from the 

 date of contamination of ar aninud by the poisou, so mauy days elapse 

 before the manifestation of the <lisease, and that such period cauuot be 

 prolonged beyond a definite and ascertained limit; nevertheless there 

 are important data which indicate that, from the period of arrival of a 



