EXCRETIONS 



511 



COMPARATIVE IMPORTANCE OF THE INTESTINE AND KIDNEYS AS EXCRETORY CHANNELS 



Although normally very little chlorid is eliminated by the intestine, the 

 amount found in the stools may be considerably increased in diarrhea. 

 About one-third of the total phosphorus output of the intestine and 

 kidneys is found in the stools. The percentage output in the feces of 

 both calcium and magnesium is high, due probably to the lactovegetarian 

 diet, which resulted in a poor absorption of compounds of these elements. 

 On a mixed diet about 60 per cent of both calcium and magnesium are 

 ordinarily eliminated in the feces of adults, although on milk diets the 

 stools of infants may contain considerably more than 90 per cent of 

 these elements. As might be anticipated from our knowledge of potassium 

 salts, a very appreciable amount of this element is eliminated in the 

 feces, and diarrhea considerably accentuates this elimination. Although 

 diarrhea very definitely reduces the absorption of nitrogen, sulphur, 

 chlorin and potassium, it appears to be almost without influence on the 

 phosphorus, calcium and magnesium. 



It is evident, therefore, that calcium, magnesium and iron are nor- 

 mally eliminated chiefly by the intestine. Failure of absorption is par- 

 tially responsible for this, but in part, these elements are secreted into the 

 intestines, as are such similar elements as strontium and barium (Mendel). 

 The elimination of calcium and phosphorus are interrelated both as to 

 total excretion and path of elimination. An increased ingestion of either 

 causes an increased elimination of tbe other at the expense of the body's 

 store, if necessary. Proportionate increase in the intake of both increases 

 the fecal excretion. Marked deviation in the balance of calcium and 

 phosphorus partially diverts the elimination of the more abundant through 



