THE CHEMISTRY OF THE ANIMAL BODY. 525 



the intimate relation between calcium salts and the functional activity of 

 protoplasm. Howell 1 believes that calcium salts furnish the primary stim- 

 ulus for the contraction of the heart. 



Calcium in the Body. — Calcium salts are especially needed in childhood for the 

 growth of the bones. It has been estimated that the human suckling requires 0.32 gram 

 CaO daily, and in the milk for that time is contained 0.55 gram to 2.37 grams, so that 

 there may easily be lack of CaO when absorption is unfavorable. In children with rickets 

 the bones contain too little calcium, and are abnormally weak and flexible. This same con- 

 dition maybe reproduced in young growing dogs by feeding them entirely on meat and fat, 

 which contain too little calcium for proper skeletal development. 2 Such dogs grow rapidly 

 in size, especially around the thorax, while the pelvis remains ludicrously small, the extrem- 

 ities become bent and finally incapable of supporting the weight of the body. A puppy 

 of the same litter fed on the same food but with the addition of bones grows normally. In 

 certain cases even when children are fed with sufficient calcium they still have the rickets. 

 This might be due to a lack of ability to absorb the salts, but this Riidel 3 has disproved. 

 To a child having rickets he administered a calcium salt, and confirmed its absorption 

 by the increase in the calcium contents of the urine, the result being the same as with 

 a normal child. (Example: Normal day, 0.0196 gram CaO in urine; after feeding 

 1.4 grams CaO dissolved in acetic acid the amount in the urine rises to 0.0396 gram for 

 the twenty-four hours. ) Riidel therefore concludes that the cause of rickets may be in a 

 local change of the bones themselves, whereby calcium salts are not deposited in the normal 

 manner. 



In osteomalacia there occurs a solution of the salts of the bones in adult life, called 

 softening of the bones. In osteoporosis, which is a simple atrophy of the bones, similar 

 effects are produced. Voit* fed a pigeon for a year on washed wheat and distilled water. 

 at the end of which time the pigeon apparently did not differ from the normal bird. A 

 few months later a wing was broken, and the autopsy discovered osteoporosis in high 

 degree, the skull being especially attacked. Weiske 5 has shown that rabbits ultimately 

 die when fed on oats which are poor in calcium ; the oats yield an acid ash and produce an 

 acid urine. On autopsy osteoporosis is found. This does not take place when calcium 

 carbonate is added to the food. Whether the loss of salts to the bone is due ton normal 

 metabolism, or to solution due to the production of acids in the metabolism of proteid, 

 is an unanswered problem (see pp. 506, 511) the discussion of which lack of space forbids. 6 

 In such experiments as the above, the percentage of ash is always diminished, while the 

 percentage of organic matter always rises, whereas the actual percentage composition of the 

 ash itself remains the same. This is a strong argument in favor of the view that bone is 

 a mineral of definite chemical composition. The mineral matter of bone is believed by 

 some to be loosely combined with the organic material, principally ossein, but of this there 

 is no proof. 



The exact amount of calcium salt necessary to keep up the supply in the adult body is 

 unknown, but it must be exceedingly small. A dog of 3.8 kilograms eating with his food 

 0.043 gram CaO maintains his calcium equilibrium (Heiss). 



Regarding the absorption of calcium salts, it has long been questioned 

 whether inorganic salts can lie absorbed, since, it was argued, insoluble 



1 American .four/nil of Physiology, 1898, vol. '_', p. 17. 



2 E. Voit : ZeiUchriftfSr Biologie, 18S0, Bd. 16, S. 70. 



3 Archiv fur exper. Pathologie und Pharmakologie 1893, Bd. 33, S. 90. 

 1 Hermann's Handbueh, 1881, vi. 1, 8. 379. 



• Zeitschriftfur Biologie, 1894, Bd. 31, 8. 421. 



6 See Weiske, Loc.cit.; Bunge, Physiologische Chemie, :!<1 ed., 1894, S. 104; V. Noorden, Path- 

 ologie der Stoffweehsels, 1893, S. 48 and 413. 



