r.KNI':RAL COXSIDICRATION OF DISl-'.ASn;. 35 



Health lias been defined as that condition in which the normal 

 structure and functions of all the component parts of an or- 

 ganized being- are maintained. 



Di:-ease is a functional or structural deviation from the normal. 

 It is that condition in which an tirganism cannot accustom itself to 

 its environments Health and di.-ease arc, however, only relati\x 

 terms, because of the flifficulty of determining a normal standard. 

 The two conditions necessarilv overlap. 



Diseases mav be classJned in manv wavs, as local and general, 

 infectious and non-infectious, inherited and acquired, etc. 



Initerited dise.ases are those transmitted from the parent in 

 spermatozoa or ova and are present at the time of fertilization. Cer- 

 tain characteristics are transmitted from parent to offspring such as 

 genus, breed and individual peculiarities. Thus horses have peculi- 

 arities so fixed and constant that ihey are transmitted to their off- 

 spring and differentiate them from other species of the genus Erjuus. 

 lireeds are differentiated b)' certain peculiarities ; thus Jersey cattle 

 are brown to light fawn in color \\-ith a l^rown muzzle, horns turned 

 in and up, they are small, lean, dish faced, etc., all of which are 

 peculiarities that distinguish them from other lireeds of cattle. 

 There are individual peculiarities, some of which are the result 

 of the fusion of parental characteristics; thus the offspring may 

 be of solid color, the result of the fusion of different parental 

 colors, (color blending), or they may be piel^ald, indicating fail- 

 ure of color blending (mosaic coloring). The extent of intensi- 

 fication of inherited generic, breed or individual peculiarities de- 

 pends upon the prepotency of the parental stock. This pre- 

 potency depends upon the length of time that the type has 

 existed under similar circumstances. The foregoing illustrates 

 Avhat is meant by the term "heredity", and demonstrates that 

 the breeding of stock is a science. 



Diseases are rarely inherited, first, because diseased spermato- 

 zoa and ova are probably incapable of fertilization, and second, 

 there is always a tendency to abort when the embryo or foetus 

 is diseased. A predisposition may be inherited, i. e., the progeny 

 of diseased parents may be more susceptible to disease than the 

 progeny of a healthy parentage. Infectious diseases are very 

 rarely "inherited. It has been demonstrated that spermatozoa 

 are not phagocytic in action and probably ova have no pliago- 

 cytic tendencies ; the latter, however, has not been proven. The 

 quantity of semen and the number of spermatozoa per given 

 volume varies in different animals and in the same animal under 



