CONTAGIOUS DISEASES OF SWINE. 491 



SPORADIC DISEASES OF HOGS. 



The hog in his natural state is ahnosit free from disease. His 

 power to resist disease has been greatly lessened by continual 

 close breeding and improper treatment. An injudicious prac- 

 tice of crossing has been carried to such an extent as to almost 

 obliterate traces of the original breed. An attempt has been 

 made to improve upon nature, to make a permanent stock that 

 will reproduce itself, which has proven a failure. All hogs be- 

 long to one great family, and it is a law of nature that, where 

 great divergence has taken place from any j^arent stock, a ten- 

 dency to revert prevails. However, if a judicious system of 

 crossing be practiced, certain breeds may be improved. The 

 male may be selected carefully from some special breed, as 

 Poland China, and crossed with an opposite breed in shape and 

 habits, as the Essex. In-breeding is often practiced through 

 an effort to dbtain a perfectly pure breed of any particular 

 species. Hogs bred in such a manner are predisposed to dis- 

 eases of every sort. The custom of breeding from sow^s too 

 young is a predisposing cause of disease. The sow should not 

 be allowed to become pregnant until one year old. Before that 

 time she is growing and immature. The results of breeding- 

 young sows and in-breeding are loss of vitality and scrofulous 

 degeneracy. This is well exemplified in herds when cholera is 

 raging. 



