38 vicTKKiNAKv l^\■|•lull,()(;^■. 



Teratomata and other malformations are iliseased conditions and 

 are usnallv nf cung'enital origin. 



Piist-iiafal diseases are those ctmtracted at any time during 

 the life nf the animal after hirth, as laminitis, actinomycosis, and 

 spa\'in. 



In classifying diseases accoriling to extent, two groups are 

 usually described, viz : — , local and general. 



1. .\ Loc.M, disease is one that affects a part or organ : as urethral 

 calculi, pulmonary anthraci isis, etc. Local diseases proper remain 

 localized although the term is used in a broader sense to desig- 

 nate a circumscribed, local, morbid process that ma}- later be- 

 come generalized. Thus; tubercular infection of a group of 

 lymphatic glands is frequently spoken of as localized tubercu- 

 losis. 



2. .\ (a:xi;RAL disease, strictly speaking, is one invoking the en- 

 tire animal bod\-, as anemia, l)ut in a more restricted sense it is 

 used til designate the involvement of se\'eral parts or (irgans. 



Etiology. — Disease has Ijeen defined as an inharmonious 

 relation between an individual and its environments. This 

 definition is indicati\-e of the variuus factors concerned in the 

 productiiin of morbid processes. The causes of disease may be 

 convenient!)- sulxlivided into two groups, viz. : ]-)redis]-iosing causes 

 and exciting causes. 



PKi-:iusrosiX(; c.m'si'.s. — Predisjiosing causes are those condi- 

 tions or environments whch render animals more suscept- 

 ible to disease. 



It has long been recognized that man\- diseases of dijmestic 

 animals are due to induced variations of species that result froiu 

 selecti(in by breeders. Xew breeds of the \'arious animals are 

 produced so ra|)idly, that the indix-iduals of the new breeds are 

 more susceptible tn disease. 



Rctrofiyessiz'e changes in anatomical structures jiredispose to 

 disease. The tarsal joint of the horse is gradually changing 

 from an active to a passive structure ; this change results in a 

 tendeuc}- to ossification and ankylosis or s])a\-in formation. Pro- 

 gressive changes in various structures are responsible for some 

 diseased conditions, viz., navicular disease in the horse, or dairy 

 breeds having large udders, are more susceptible to mammary 

 diseases. Several breeds of horses are characterized by small 

 heads and esjiecially diminished facial bones, a conformation 

 that predisposes t(-i dental diseases. 



Inbrcedih.(i has lieen a cause of decreasing the resistance of 

 anin-ials to disease. 



Age. The age of animals is an important predisposing factor 



