SPLENIC OR PERIODIC FEVER OF CATTLE. 123 



cout.ict between Texan and southern or western cattle that induces the 

 malady ; and, so far as recorded observations and my own inquiries at 

 present extend, the animals contaminated by feeding on Texan trails 

 have not in a single instance propagated the disease to other animals. 

 Indeed, I have not met with one instance where sucking calves have 

 caught the affection from their dams, or from other cows which they 

 have been made to suck. Many cases have come under my observation 

 of cattle in Illinois, Indiana, and elsewhere, coming in contact with 

 Texans through a fence, by drinking in the same water, and even being 

 housed in sheds with sick natives, and yet escaping the disease. We 

 must, therefore, distinguish it from the contagious maladies alluded to, 

 and refer it to another group. 



Splenic fever is an enzootic. It originates in various parts of the 

 Gulf States. Florida cattle driven north are as dangerous as Texans, 

 deriving the same deleterious properties from the soil on which they are 

 reared, and in all probability the vegetations on which they feed. In 

 the south, si^lenic fever is distinctly indigenous, and, so far as Texas is 

 concerned, I have satisfied myself that the disease is universally preva- 

 lent in that State. 



Its complete manifestation is readily witnessed in States north of 

 31° north latitude. Here the malady can no longer be declared 

 indigenous; but there are numerous instances which can be cited, of 

 I)ui'ely enzootic diseases spreading a certain distance by contagion. Two 

 of the most marked instances are furnished us by the malignant anthrax 

 of Eussia, better known as the Siberian boil plague, and the milk-sick- 

 ness, or trembles, of the United States. 



The milk-sickness is due to cattle feeding on low woodland pastures, 

 where certain poisonous plants abound. It originates only in a very 

 limited area of country ; but the animals may travel, and their flesh and 

 milk will communicate the disease when eaten by other animals, and 

 even by human beings. Trembles is, therefore, an enzootic disorder, 

 capable of being primarily produced only in definite localties ; but the 

 poison which contaminates the food is capable, through that food, of 

 attacking a second and a third animal, or as many as partake of it. 

 There is another striking similarity between the course of milk-sickness 

 and splenic fever. The animal food, poisoned in the disease-producing 

 district, may show no signs of disease, unless subjected to a definite 

 existing cause, such as being driven or frightened. In classifying 

 trembles among the diseases of the lower animals we should undoubt- 

 edly place it among the effects of vegetable i)oisons, and study it as 

 a very remarkable toxicological phenomenon. I should be disposed 

 to deal with splenic fever in the same way. Southern cattle, accustomed 

 to feed on certain pastures in Florida and Texas, thrive, antl their sys- 

 tems become charged with principles which are thrown off in the excre- 

 tions for many weeks, and probably two or three months after they leave 

 their native soil. Herds of these animals necessarily deposit a large 



