474 A MANUAL OF PHYSIOLOGY 



It is not indifferent in what form the calcium is taken, nor can it 

 be replaced to any great extent by other earthy bases, as magnesium 

 or strontium. Weiske fed five young rabbits of the same litter on 

 oats, a food relatively poor in calcium. One of the rabbits received 

 in addition calcium carbonate, another calcium sulphate, a third 

 magnesium carbonate, and a fourth strontium carbonate. At the 

 end of a certain time it was found that the skeleton of the rabbit fed 

 with calcium carbonate was the heaviest and strongest of all, and 

 contained the greatest proportion of mineral matter. Then came 

 the rabbit fed with calcium sulphate. The animal which received only 

 oats had the worst-developed skeleton ; the condition of the animals 

 fed with magnesium and strontium carbonates was but little better. 



Milk is a food rich in calcium and also in phosphorus, a 

 circumstance evidently related to the rapid development of 

 the skeleton in the young child. As in the other natural 

 foods, the calcium and phosphorus are partly in the form of 

 organic compounds, united with the proteids and with the 

 nucleo-proteid, caseinogen, and partly in the form of 

 inorganic salts. Both of these elements are more easily 

 assimilated by the body in the organic than in the inorganic 

 form. And the same is true of iron, which exists in organic 

 combination in the bran of wheat, in the haemoglobin of the 

 blood and of muscular fibres, in the nuclei of most cells, 

 vegetable and animal, and conspicuously in the nuclein of 

 the yolk of the egg. It was supposed by Bunge that only 

 such organic compounds of iron could be absorbed, and that 

 the undoubted benefit derived from the administration of 

 inorganic iron compounds, such as ferric chloride, in anaemia, 

 was due not to their direct absorption, but to their shielding 

 the organic compounds from the attack of the sulphuretted 

 hydrogen in the intestine (p. 359). But this theory has been 

 shown to be inconsistent with the facts. For instance, after 

 the administration of salts of iron, the iron in the blood, liver, 

 spleen, and other organs increases, but there is no accumula- 

 tion of iron in the liver of an animal to which salts of 

 manganese have been given, although these are equally de- 

 composed by sulphuretted hydrogen. It is certainly the case, 

 however, that under ordinary conditions all the iron that the 

 body receives or needs is taken in the form of organic com- 

 pounds, since there is no inorganic iron in the natural food- 

 substances. Stockman, from careful estimations of the 



