20 



DIGESTION AND FOOD. 



In some countries low-bred horses suffer from a very porous 

 condition of their bones, constituting a disease termed Osteo- 

 porosis. In America it is called ' big head/ from the size 

 attained, especially by the jaw bones, which, in swelling, con- 

 tract the mouth, and soon incapacitate the animal from 

 masticating or chewing its food. The subjoined cut is from 

 a drawing I made from nature whilst in Stuttgard in 185-4. 

 I shall more fully treat of this interesting disease elsewhere. 



Kg. -8. 



SPORADIC APHTHA is a vesicular eruption of the mouth, 

 distinguished from the epizootic disease by its veiy mild form 

 and non-contagiousness. This mild affection is occasionally 

 witnessed in all animals, and was mentioned by the earliest 

 writers on veterinary medicine, such as Ruellio, Vegetius, and 

 others. It is sometimes primary, and due to causes operating 



