NUTRITION 271 



as does also prothrombin. The blood also contains consider- 

 able amounts of potassium chloride and sodium carbonate. 

 Next in abundance are phosphates of calcium, magnesium, 

 and sodium, the chief inorganic constituents of the cells being 

 potassium phosphate. In the plasma sodium chloride is the 

 most abundant salt. 



In the construction of the tissues of the growing chick, 

 calcium, phosphorus, potassium, sodium, and chlorine play 

 the most abundant part. 



Aid to Function. — The presence of calcium salts is necessary 

 for muscular contraction, and the control of both voluntary 

 and involuntary muscles is accomplished through the pro- 

 portion of calcium, magnesium, sodium, and potassium salts 

 acting upon them. Sodium salts are essential to cardiac 

 relaxation; in fact the heart cannot functionate without the 

 presence of sodium and calcium salts. The blood cannot 

 coagulate, when drawn, without the presence of calcium salts. 

 The essential alkalinity of the blood is due to the phosphate 

 and bicarbonate of sodium. Iron is essential in the red blood 

 cells to give it its oxygen carrying power, 0.4 per cent, of the 

 hemoglobin being iron. The nature of the inner stimulus 

 of the heart is intimately connected with certain organic 

 salts of sodium, calcium, and potassium. These are probably 

 in the form of chlorides. It has been shown that calcium 

 promotes contraction and that sodium and potassium bring 

 about relaxation of the heart. The sodium carbonate of the 

 blood probably assists in carrying the carbon dioxid to the 

 eUminative organs, the lungs. 



Free acid formation in the stomach of fowls is probably 

 formed by selective powers possessed by the secretive cells 

 by an interaction of sodium chloride and sodium di-hydrogen 

 phosphate of the blood. The digestive fluid secreted by the 

 glands of Lieberkilhn is alkaline due to sodium carbonate. 

 The pancreatic secretion contains much sodium, magnesium, 

 potassium, and calcium in combination with chloride, car- 

 bonate, and phosphate. Bile contains sulphur, phosphate, 

 and chloride of sodium, and salts of calcium, magnesium, iron, 

 and potassium. The larger portion of salt is sodium. The 

 salts of the body perform important functions in connection 



