26 METABOLISM OF ORGANIC AND INORGANIC PHOSPHORUS. 



The relative amounts of calcium and phosphoric acid in the teeth 

 are, according to the analysis of Hoppe-Seyler, a about the same as 

 in bone earths. 



The importance of calcium for the activity of the nervous system 

 and the muscles has been the subject of study by many investigators. 

 The conclusions drawn are that if the, amount of calcium is decreased 

 nervous and muscular irritability will result and, conversely, that an 

 increase of the calcium will diminish the irritability of the nerves and 

 muscles. Ringer proved that the frog's heart can be kept beating 

 for long periods upon a mixture of sodium chlorid, potassium chlorid, 

 and calcium phosphate or chlorid, and he laid especial importance 

 upon the calcium. The calcium ions are present in relatively small 

 quantities in the blood, but they are absolutely necessary to con- 

 tractility and irritability. When present in quantities above normal 

 or when in proportional excess over the sodium or potassium ions 

 they cause a condition of tonic contraction that has been designated 

 as calcium rigor. The calcium promotes a state of contraction, the 

 sodium and the potassium a state of relaxation. 



Tigerstedt in his text-book states that calcium salts favor the con- 

 traction of the heart, while potassium salts are important for its 

 relaxation. Calcium favors muscular movements of low forms of 

 animal life the contractility of both skeletal and smooth muscles. 

 He cites the experiments of Voit, 6 who fed pigeons with food con- 

 taining no calcium, and found that the bones which were used for 

 movements were normal for calcium, while the sternum and skull 

 bones were brittle and even perforated in places. 



Falta and Whitney c showed that after extirpation of a dog's 

 pancreas, the calcium elimination was increased, though the nitro- 

 gen, phosphoric acid ratio remained unchanged. The excretion of 

 uric acid in these cases was doubled. 



The importance of calcium salts for the growing organisms is dis- 

 cussed by Aron and Sebauer. d Special attention was given to the 

 calcium content of the bones, brains, nerves, muscles, and blood. 

 Dogs and rabbits were used, half of them being fed on a calcium-poor 

 diet. The young animal requires at least 1.2 per cent of its body 

 weight of calcium; a diet supplying a smaller amount is called a 

 calcium-poor diet. Under such conditions .nervous and other dis- 

 orders follow, a condition like rickets being established after con- 

 tinued feeding of such a diet; in these cases the bones contain more 

 water than is normal, that is, a water-rich bone is developed whose 



Hammarsten, Textbook of Physiological Chemistry, New York, 1908, p. 440. 



&Zts. Biol., 1880, jftf :55. 



c Beitr. chem. Physiol. Path., 1908, 11 : 224. 



d Biochem. Zts., 1908, 8:1. 



