232 A MANUAL OF VETERINARY PHYSIOLOGY 



Faeces always float in water so long as cohesion is maintained. 

 The colour of the faeces in the horse is yellowish or brownish red, 

 in the ox greenish-brown ; they rapidly become darker on ex- 

 posure to the air. When the animal is grass-fed the faeces are 

 green, and when a horse is fed wholly on corn they become very 

 yellow, and like wet bran in appearance. The colour of the 

 faeces of animals receiving hay or grass is due to altered chloro- 

 phyll. The faeces of the horse are moulded into balls in the single 

 colon. They are always acid in reaction, the acidity probably 

 depending upon the development of some acid from the carbo- 

 hydrates of the food. 



Faeces contain lignin amongst the indigestible portion of the 

 ingesta, a proportion of cellulose, husks of grains, the downy hair 

 found on the kernel of oats, vegetable tubes and spirals, starch 

 and fat granules, gums, resins, chlorophyll, etc. ; unabsorbed 

 protein, carbohydrate and fatty matters ; products of digestive 

 fermentation, such as lactic, malic, butyric, succinic, acetic, and 

 formic acids ; leucine, tyrosine, indol, skatol, and phenol ; biliary 

 matters and altered bile pigment — stercobilin — which gives the 

 colour to the dejecta in the dog, but not in herbivora ; and, lastly, 

 mineral matter in varying proportions. In the dog portions of 

 muscle fibre, fat-cells, tendinous and fibrous tissue, are found in 

 animals fed on flesh. 



Of the inorganic matter silica exists in largest amounts in 

 herbivora, then potassium and phosphates ; sodium, calcium, 

 magnesium, and sulphates, form a smaller but still important 

 proportion. The horse excretes but little phosphoric acid by the 

 kidneys, but considerable quantities pass with the faeces in the 

 form of ammonio-magnesium phosphate. This salt is derived 

 principally from the oats and bran of the food, and it frequently 

 forms calculi through collecting in the colon around a pebble or 

 nail as a nucleus, and becomes mixed with organic substances. 

 Other intestinal calculi are formed from lime deposits in the bowel, 

 while collections of the fine hairs from the kernels of oats become 

 encrusted with ammonio-magnesium phosphate, and form oat- 

 hair calculi. In the Persian wild goat and certain antelopes 

 intestinal concretions are found known as Bezoar stones, formerly 

 much used in medicine, and as antidotes to poison. There are 

 two varieties of calculi, one olive-green, the other blackish- 

 green. The first melts when heated, emits aromatic fumes, 

 and consists chiefly of an acid allied to cholalic acid. The 

 chief constituent of the second variety is an acid derivative of 

 tannic acid, which indicates their origin from food substances. 

 Stomach calculi have not been unknown in the horse, while in 

 cattle, as the result of licking each other, * hair balls ' are 

 common objects. 



