494 DISEASES OF THE HOESE. 



fevers, in which there are alterations of exacerbations of the febrile 

 symptoms and remissions, in which the body returns to its normal 

 condition or sometimes to a depressed condition, in which the func- 

 tions of life are but badly performed; and continued fevers, which 

 include contagious diseases, such as glanders, influenza, etc., the septic 

 diseases, such as pyemia, septicemia, etc., and the eruptive fevers, 

 such as variola, etc. 



Whether the cause of the fever has been an injury to the tissues, 

 such as a severe bruise, a broken bone, an inflamed lung, or excessive 

 work, which has surcharged the blood with the waste products of the 

 combustion of the tissues, which were destroyed to produce force, or 

 the toxins of influenza in the blood, or the presence of irritating ma- 

 terial, either in the form of living organisms or of their products, 

 as in glanders or tuberculosis — the general train of symptoms are 

 much the same, varying as the amount of the irritant differs in 

 quantity, or when some special quality in them has a specific action 

 on one or another tissue. 



There is in fever at first a relaxation of the small blood vessels, 

 which may have been preceded by a contraction of the same if there 

 was a chill, and as a consequence there is an acceleration of the cur- ' 

 rent of the blood. There is, then, an elevation of thfe peripheral 

 temperature, followed by a lowering of tension in the arteries and 

 an acceleration in the movement of the heart. These conditions may 

 be produced by a primary irritation of the nerve centers of the brain 

 from the effects of heat, as is seen in thermic fever, or sunstroke, or by 

 the entrance into the blood stream of disease-producing organisms 

 or their chemical products, as in anthrax, rinderpest, influenza, etc. 



There are times when it is difficult to distinguish between the exist- 

 ence of fever as a disease and a temporary feverish condition which 

 is the result of excessive work. Like the condition of congestion of 

 the lungs, which is normal up to a certain degree in the lungs of a 

 race horse after a severe race, and morbid when it produces more than 

 temporary phenomena or when it causes distinct lesions, the tem- 

 perature may rise from physiological causes as much as four degrees, 

 so fever, or, as it is better termed, a feverish condition, may follow 

 any work or other employment of energy in which excessive tissue 

 change has taken place ; but if the consequences are ephemeral, and 

 no recognizable lesion is apparent, it is not considered morbid. This 

 condition, however, may predispose to severe organic disturbance 

 and local inflammations which will cause disease, as an animal in this 

 condition is liable to take cold and develop lung fever or a severe 

 enteritis, if chilled or otherwise exposed. 



Fever in all animals is characterized by the same general phe- 

 nomena, but we find the intensity of the symptoms modified by the 

 species of animals affected, by the races which Bubdivide the species, 



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