132 THE DOG IN DISEASE. 



indicated nearly always by more or less elevation of tem- 

 perature, as well as other changes. 



Locally the exudation from the vessels, the cells that 

 pass from them, and those that are produced in the neigh- 

 boring tissues, may collect to form an abscess. 



An inflammation may end in resolution or return to 

 the normal without formation of abscess, etc., or result 

 in abscess, gangrene, or death of parts when very severe, 

 softening and disintegration, and various forms of degen- 

 eration; or poisonous products may be formed, taken 

 into the general circulation, and cause the most serious 

 disturbance, or even death. 



ffypercemia may lead to increased growth, or may go 

 on to inflammation or return to the normal. 



Venous congestion is very apt to issue in some form of 

 " exudation " i. e., a fluid derived from the plasma of the 

 blood, allied to it in general composition, but to be re- 

 garded as " foreign " in a considerable degree. By press- 

 ure and otherwise it may do much harm. 



The Causes of Disease. Any sudden and great altera- 

 tion in the environment is apt to be followed by such 

 inability on the part of the organism to adapt itself to it 

 that what we term disease arises. Prominent among these 

 are extremes of temperature, too little and too much food, 

 over-exertion, etc. Such are to be classed among predis- 

 posing causes in most instances. 



Of late our knowledge of disease has been greatly 

 extended by the study of a world of extremely minute 

 vegetable organisms by means of powerful lenses, artificial 

 cultures, and other kinds of experiments. 



It has been shown that animal life may be preyed upon 



