FUNDAMENTAL PRINCIPLES OF DISEASE. 39 



blood vessels, and is distributed to distal partes. Essential fevers are 

 those in which there is from the outset a general disturbance of the 

 whole economy. This may consist of an eUMuentary alteration in the 

 blood or a general change in the constitution of the tissues. Fevers 

 of the latter class are usually due to some infecting agent and belong, 

 therefore, to the class of infectious diseases. 



Essential fevers are subdivided into ephemeral fevers, which last 

 but a shoii, time and terminate by critical pheftomena; intermittent 

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

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

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

 tions of life are but badly j^erformed; and continued fevers, which 

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

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

 such as variola, etc. 



AVhether the cause of the fever has been an injury to the tissaies, 

 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 

 (juantity, 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 b}' 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 the 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, ant I morbid when it produces more than 

 temporai-y phenomena or when it causes distinct lesions, the tem- 

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

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

 any work or other employment of eneigy in which excessive tissue 



