230 A Manual of Veierina/ry Physiology. 



and the amount of salts passing away with the f;eces and 

 of no use to the system was nearly half that ingested. 



The salts in the body perform important functions in 

 connection with secretion and excretion ; as Foster ex- 

 presses it, they 'direct the metabolism of the body.' Their 

 distribution throughout the structure is remarkably regular, 

 sodium and chlorides being found in the blood-serum, potas- 

 sium and phosphates in the red cells, sulphur in horn, 

 potassium in sweat, phosphates and lime in bones, etc. 

 When a deficiency in salts occurs, the body apparently for 

 some time draws on its own store, and then certain nutri- 

 tive changes follow. Both organic and inorganic salts are 

 required. 



I have drawn attention to the remarkable fact that 

 potassium is largely the salt used by herbivora, and sodium 

 only slightly so (p. 20) ; and further, that horses can be kept 

 in perfect condition without receiving sodium chloride with 

 their food, that which is naturally in it (and the amount is 

 small) being quite sufficient for the uses of the economy.* 



Starvation. — When an animal is starved it lives on its 

 own tissues ; in the herbivora the urine becomes acid , 

 hippuric is replaced by uric acid, and the secretion becomes 

 clear. The elimination of nitrogen in the starving animal 

 at first falls rapidly, then gradually, and shortly reaches a 

 fluctuating daily quantity. 



During starvation the C0 2 excreted falls in amount, and 

 the oxygen absorbed becomes reduced, though not in pro- 

 portion to the fall of the C0 2 . 



If water be given, life is considerably prolonged. Colin 

 records a case (to be mentioned presently) where a horse 

 receiving water lived thirty days without food. The loss in 

 weight by starvation consists of two-thirds water, one-twelfth 

 albumin, and one-fourth fat. It is notorious that herbivora. 

 though they lose less proteid during starvation than car- 

 nivora, yet do not withstand starvation so well. Nor need 

 we go so far as a starvation experiment to ascertain this 

 fact: when men and horses are being worked hard, whether 

 * Journal of Physiology, vol. xi., No. 6. 



