INTEODUCTION. 61 



epizootics and other specific disorders of a highly destruc- 

 tive character, will induce any disease which occurs to 

 assume a low type. The drinking water supplied to an 

 animal may be so impure as to originate or communicate 

 disease. Besides the conditions already mentioned, age, 

 sex, and conformation determine individual liability to 

 disease. Young animals respire quickly, have a quick pulse, 

 and high internal temperature, they are particularly liable to 

 diseases of growth, to acute inflammations, and to catarrhal 

 affections of the alimentary and respiratory tracts, also 

 their constitutional energy is hardly able to check and 

 counteract the ravages of entozoa. In adult animals the 

 tendency is to certain disorders resulting from diet, also to 

 diseases of the generative system. In old animals we 

 find the effects of deficient energy of the heart and 

 degeneracy of blood-vessels ; hence metastatic congestions, 

 senile gangrene, and heart disorders occur especially in 

 them. Male animals are most liable to acute disorders, 

 as being endued with higher vital energy than females. 

 Castration materially modifies constitutional conditions, 

 and secures immunity from such acute disorders of the 

 generative organs as occur in the entire animal, facilitates 

 fattening, and lessens liability to injury. It causes the 

 disorder known as pelvic hernia or " gut-tie.^^ Females 

 run the risks of parturition and lactation, their respira- 

 tory, circulatory, and nervous functions are generally less 

 active than those of the male. Conformation and the 

 uses to which the animal has been put have marked 

 effects as predisposing causes ; thus, the shortness of 

 the neck of the ox accounts for his frequent attacks of 

 apoplexy, and too free exercise of generative powers 

 will bring about atrophy of the bulFs testes. Previous 

 disease of an organ predisposes it to renewal of an attack. 

 Sometimes only imperfect repair occurs, and the partially 

 formed tissue is liable to again become the seat of morbid 

 changes, even without the action of any appreciable 

 excitant. Recurrent abscesses are of this nature, as also 

 certain forms of dysentery. Exciting causes are varied, 

 such as exposure to currents of cold air, sudden transition 



