IX ORGAN 1C SUBSTANCES. 43 



rough and tangled hide, and a dull, inexcitable disposition, while in 

 those which had received the additional ration of salt the hide was 

 smooth and glistening, and the general appearance was vigorous and 

 animated. While these animals, therefore, may subsist for a time 

 upon the salt naturally contained in their food, an additional quantity 

 is required to maintain the system in good condition for an indefinite 

 period. 



There is a similar necessity for salt as an addition to the food of the 

 human species. No other condiment is so universally employed ; and 

 its use seems to be based upon an instinctive demand of the system for 

 a substance which is necessary for the full performance of its functions. 

 Beside other properties, it no doubt acts in a favorable manner by 

 exciting the digestive secretions, and by assisting in this way the solu- 

 tion of the food. Food which is tasteless, however nutritious in other 

 respects, is taken with reluctance and digested with difficulty ; while 

 the attractive flavor developed by cooking, and by the addition of 

 salt and other condiments, excites the secretion of the saliva and gastric 

 juice, and thus facilitates digestion. The sodium chloride taken with 

 the food is afterward absorbed from the intestine, and deposited in 

 various quantities in different parts of the body. 



Notwithstanding various surmises which have been presented as to 

 its possible decomposition and the recombination of its elements in the 

 body, we have no certain knowledge of such changes taking place in 

 the sodium chloride while a constituent part of the animal frame. It 

 passes from the alimentary canal to the blood, from the blood to the 

 tissues, and is finally discharged with the urine, mucus, and cutaneous 

 perspiration in solution in these fluids. Under ordinary circumstances, 

 much the largest proportion passes out by the kidneys. The entire 

 quantity of sodium chloride discharged with the excretions by an adult 

 man is about 15 grammes per day ;* of which 13 grammes are contained 

 in the urine, and 2 grammes in the perspiration. Thus, of all the 

 sodium chloride contained in the body, considerably more than ten per 

 cent, passes through the system in twenty-four hours. This plainly 

 indicates its activity and importance in the internal changes of nu- 

 trition. 



6. Potassium Chloride, KC1. 



This substance is found in many, if not all, of the animal tissues 

 and fluids, accompanying the sodium chloride, with which it is closely 

 related in its physiological characters. It is especially abundant, as 

 compared with sodium chloride, in the muscles and in the milk, less so 

 in the blood, the gastric juice, the urine, and the perspiration. Both 

 salts are neutral in reaction, and are retained in the liquid form in 

 the blood and secretions by solution in the water of these fluids. 

 Potassium chloride is introduced as an ingredient of both animal and 



* Neubauer und' Vogel : Analyse des Harris. Wiesbaden, 1872, p. 54. Beneke: 

 Pathologic des Stoffwechsels. Berlin, 1874, p. 322. 



