CAUSES OF DISEASE. 9 



and size have much to do with. Ossification of the lateral 

 cartilages is rarely witnessed in the Letter bred, but is very 

 common in the cart-horse. Navicular disease, so rife amongst 

 better bred horses, is a very rare cause of lameness in the cart- 

 horse ; and, not to adduce too many examples, high-bred, nervous 

 animals are more liable to nervous diseases than those of a lower 

 breed. 



The effects of colour in predisposing to disease are very curi- 

 ous, as shown in the frequency of melanoid sarcomma, and in 

 the intractability of tumours which do not contain pigment in 

 grey or white horses ; and the liability to cutaneous eruptions 

 upon the white parts of the body only has caused one disease to 

 be called " white face and foot disease." — (Crusta labialis, see 

 Veterinary Surgery.) 



Tribe or speeies. — The influence of species in favouring or 

 resisting certain forms of disease is really remarkable. Thus the 

 horse, wliilst liable to glanders, resists diseases to which cattle 

 and sheep are peculiarly liable, such as rinderpest, pleuro-pneu- 

 monia, eczema epizootica. Eabies, again, is primarily a purely 

 canine disease. Charbonous disease is transmissible to man and 

 to all the domesticated animals, with the exception of the domestic 

 fowls and birds generally ; but here it has been found — and 

 probably this discovery explains why some contagia affect 

 certain animals only — that resistance to charbonous contagion is 

 due, not to conformation, but to temperature ; for when the tem- 

 perature of the fowl has been lowered by removing its feathers 

 and keeping it in water, it has become affected with the disease. 



Teminrament, which consists in excess of or defect in some 

 function or set of functions, certainly predisposes to particular 

 diseases. 



The sanguine temperament, implying an activity of the circu- 

 latory and blood-producing organs, tends to diseases of an 

 inflammatory character. This temperament is best exhibited in 

 highly bred horses, whereas in lower bred animals the lym- 

 phatic temperament seems to predominate. In this tempera- 

 ment there is a deficiency of arterial tonicity, a want of nervous 

 power, the circulation is languid, the capillaries and lymphatics, 

 particularly in the extremities and depending parts of the body, 

 are often congested and the limbs oedematous, which conditions 

 disappear for a time with exercise. Inflammatory diseases 



