190 PRINCIPLES OF VETERINARY SCIENCE 



waste products faster than the excretory organs can dispose of 

 them. This results in those conditions known as fatigue and 

 exhaustion from which recovery is slow or incomplete and which 

 predispose to disease. 



(7) Lack of exercise and confinement to close, ill-ventilated 

 stables are more detrimental than allowing free range with no 

 protection. Interference with the blood supply and nourish- 

 ment in all parts of the body occurs when animals are deprived 

 of daily exercise. The results are seen as swollen legs, constipa- 

 tion and indigestion. 



(8) Age has a marked influence in the development and foster- 

 ing of special forms of disease. The foal and calf suffer from 

 diseases that the adult horse and cow are immune to, because the 

 defensive properties of their bodies are not fully developed. In 

 advanced age there is a predisposition to rheumatic affections 

 and joint diseases. 



(9) Sex influence is confined to the diseases of the generative 

 organs and to them only insofar as they differ in structure and 

 function. For example, the uterus and udder of cows are par- 

 ticularly suited to the growth and development of the germs that 

 cause contagious abortion, but these organisms seldom infect 

 the bull's reproductive organs because no suitable place for the 

 growth of the abortion bacilli is found in them. Males are 

 especially liable to urethral calculi. Otherwise males and females 

 are equally liable to all affections of their species. 



(10) Other diseases, as well as a previous attack of the same 

 disease, may influence the development of subsequent diseases. 

 This is seen in pneumonia which sometimes weakens the resistive 

 powers of the animal and renders it more liable to successful 

 attack by tuberculosis and other infections. One attack of 

 founder makes the horse susceptible to a second attack. For- 

 tunately, if an animal has passed through an acute infectious 

 disease it is usually protected from further attack by the same 

 disease, for a time at least. 



(11) Hereditary predispositions to disease are derived from one 

 or both parents. For this reason breeding animals that are in- 

 bred, immature, too closely related, or weakened from any cause 

 will predispose the offspring to disease. Just how these factors 

 affect the animal are matters that are fully taken up in courses in 



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