ETIOLOGY— CAUSES OF DISEASE 221 



by the employment of appropriate remedies. The chemical agencies which 

 act as intrinsic causes of disease will include those which have just been 

 referred to, with the addition of all poisonous agents either belonging to 

 the organic or the inorganic classes, and all the deleterious products re- 

 sulting from deranged digestion or from imperfect oxidation. Of the effete 

 products which are thus converted into animal alkaloids and extractives, 

 the disastrous effects have already been adverted to under the heading of 

 predisposing causes. 



Food. — In respect of the influence of solid and liquid food, the lower 

 animals are favourably situated iu comparison with the human subject, as, 

 in a state of domestication, horses and other animals which are used in the 

 service of man are not permitted to exercise their own taste in the selection 

 of their diet, but are supplied by their owners with the amount and quality 

 of alimentary matters w T hich are selected with the distinct intention to 

 produce certain desired results. It may happen, however, that in carrying 

 this intention into effect the food may act as an exciting cause of disease 

 owing to an excess of certain constituents. Thus, in the case of animals 

 which are kept for the purpose of being fattened, serious disturbance of 

 certain organs, especially of the circulatory and respiratory systems, may 

 be occasioned in consequence of the excessive quantity of fatty material 

 which is deposited in the structure of important organs such as the liver 

 and heart. Serious results may also follow the consumption of adulterated 

 alimentary matters, which are, as a matter of fact, only given in ignorance, 

 and may therefore be looked upon as accidental causes of disease, which 

 could be avoided by the exercise of care on the part of the attendant. In 

 the case of the horse, the food is generally of a very simple nature, consist- 

 ing of hay, oats, beans or peas, bran, and, incidentally, green food and 

 carrots. None of these articles of diet lend themselves to any process of 

 adulteration; but some of them, oats and hay particularly, may become 

 dangerous in consequence of changes which take place during fermentation, 

 or from the growth of certain moulds, or from accidental contact with the 

 virus of infective diseases. Mouldy hay, and oats which have been damaged 

 by water and afterwards kiln-dried, commonly produce serious and some- 

 times fatal effects. The condition of these articles of food is easily recognized, 

 and their use may consequently be readily avoided; but in the case of 

 accidental contamination with the infective matter of anthrax or other 

 contagious disorders there is little probability of the fact being discovered 

 until the animal exhibits indications of the disease, and even then the con- 

 taminated food may altogether escape suspicion. Deficiency of food is a 

 predisposing cause of disease, but when it amounts to extreme privation it 

 becomes an exciting cause. The immediate consequences are lowering of 



