LAW OF SIMILARITY. ' 31 



to inhale noxious efiBuvia, and to eat unsuitable food, 

 we cannot wonder either that they become victims of 

 disease or transmit to their progeny a weak and sickly 

 organization. Swine are not naturally the dirty beasts 

 which many suppose. "Wallowing in the mire," so 

 proverbial of them, is rather from a wish for protection 

 from insects and for coolness, than from any inherent 

 love of filth, and if well cared for they will be compara- 

 tively cleanly. 



The practice of close breeding, which is probably 

 carried to greater extent with swine than with any 

 other domestic animal, undoubtedly contributes to their 

 liability to hereditary diseases, and when those possess- 

 ing any such diseases are coupled, the ruin of the stock 

 is easily and quickly effected, for as already stated, 

 they are propagated by either parent, and always most 

 certainly and in most aggravated form, when occurring 

 ia both. 



With regard to hereditary diseases, it is eminently 

 true that " an ounce of prevention is worth a pound of 

 cure." As a general and almost invariable rule, ani- 

 mals possessing either defects or a tendency to disease 

 should not be employed for breeding. If, however, for 

 special reasons it seems desirable to breed from one 

 which has some slight defect of symmetry, or a faint 

 tendency to disease, although for the latter it is doubtful 



