INORGANIC SALTS, STIMULANTS, AND CONDIMENTS. 923 



the sodium chlorid. Thus, if potassium sulphate were added to 

 the blood it would react with sodium chlorid, giving some potas- 

 sium chlorid and some sodium sulphate. Both of these salts 

 will be removed by the kidneys, since, except in minute amounts, 

 they are, so to speak, foreign to the blood. This latter liquid 

 will thereby lose some of its supply of sodium salt, whence the 

 craving for more in the food.* The content of the blood in sodium 

 chlorid remains remarkably constant. When an excess is taken in 

 the food it is removed by the kidneys. On a salt-free diet or 

 in starvation the amount of sodium chlorid secreted in the urine 

 soon falls to a low figure (0.6 gm.), showing that the tissues are 

 holding on to this constituent. It cannot be doubted, however, 

 that under ordinary conditions we use salt in quantities much larger 

 than is necessary to maintain the sodium chlorid content of the 

 blood. It is employed as a condiment for its pleasant flavor, and it 

 is possible that its use is often carried to excess. It can be shown, 

 in fact, that by increasing the intake of salt an edematous condition 

 of the tissues may be produced, owing to the fact that the salt 

 increases the osmotic pressure in the tissues. So also in conditions 

 of edema or inflammation restriction of the salt of the diet may give 

 the contrary result and help to restore the tissues to a normal state 

 as regards their water contents. 



The calcium salts of the body play a most important role in 

 connection with the irritability of muscle and nerve (p. 570). 

 They are also of obvious importance in furnishing material for 

 the growth of the skeleton. Their importance in this regard has 

 been demonstrated by feeding experiments. Young dogs when 

 given a diet poor in calcium salts fall into a condition resembling 

 rickets in children, owing to a deficient growth of the bones. Pig- 

 eons also, when fed upon a similar diet, exhibit an atrophy and 

 fragility of the bones due doubtless to the lack of calcium salts. 

 As in the case of the other food materials, there must be a definite 

 calcium metabolism in the body. It is probable, indeed certain, 

 that most of the calcium salts ingested simply pas$ through the 

 body without entering into its structure. They are eliminated 

 unchanged or unused in the feces or urine. A small portion, how- 

 ever, must be absorbed and used and a corresponding amount must 

 be eliminated as a true waste product of tissue metabolism. Voit, 

 by experiments upon isolated loops of the intestine, has shown 

 that some calcium is constantly eliminated from the inner surface 

 of the intestine. The amount is small, not exceeding perhaps 0.15 

 to 0.16 grams per day. There is some evidence that the amount 

 of calcium in the tissues increases with age. This is certainly 



* For an interesting discussion, see Bunge, "Physiologic des Menschen," 

 vol. ii., p. 103, 1901. 



