400 ARSENIC, ANTIMONY AND PHOSPHORUS 



the secondary or normal glycerophosphates. The second variety is 

 the one most used in medicine. Those of calcium and sodium are 

 generally preferred. ' 



Calcii Glycerophosphas. Calcium Glycerophosphate occurs as 

 a white, odorless and almost tasteless powder, soluble in water, al- 

 most insoluble in boiling water, soluble in dilute acids but insoluble 

 in alcohol or ether. Dose for the dog is 5 grains in powder, capsule 

 or tablet. 



Sodii Glycerophosphas. Sodium Glycerophosphate occurs in 

 white, monoclinic plates or scales, odorless, of a saline taste, soluble 

 in water, insoluble in alcohol. Doses same as for the above. 



These salts were introduced in medicine as substitutes for the 

 phosphates and hypophosphites, on the ground that they were more 

 rapidly assimilated, since they more nearly resemble lecithin in com- 

 position, than do the others. Their si^periority has not been sub- 

 stantiated experimentally or clinically and it is doubtful if they 

 have any advantage over the inorganic phosphates in phosphorus 

 metabolism. They are useful in exhaustion, slow or tardy con- 

 valescence, and neurasthenia as " nerve tonics." 



LECITHIN 



Lecithin consists of glycerophosphoric acid and a fatty acid com- 

 bined with choline. It contains about 4 per cent, of phosphorus. 

 Lecithin is a constituent of plant and animal tissues, especially of 

 nervous tissue and yolk of eggs. The lecithins vary somewhat in 

 composition according to their source, but this does not appear to 

 effect their action. Animals take in fairly large amounts of lecithin 

 with their food and there is no evidence to show that small daily 

 doses are necessary when a good diet is available. 



NUCLEIN 



ISTucleins are combinations of proteids with nucleic acid and are 

 derived from the nucleoproteids of cells. The term " nuclein " is 

 often carelessly employed, being frequently used when nucleic acid 

 is meant. Cells in general are rich in nucleoproteids. The best- 

 known varieties are those obtained from wheat embryo and yeast. 

 The composition of the nucleins of commerce varies greatly, accord- 

 ing to their method of preparation, but the nucleic acids are definite 

 complex chemical compounds. JSTucleic acid from yeast, the usual 

 commercial variety, contains about 10 per cent, of phosphorus. 



The nucleins and nucleic acids were introduced as remedies for 

 tuberculosis in man. They have been claimed to increase the num- 

 ber of white corpuscles and consequently were recommended in the 

 treatment of infectious diseases, but their usefulness in these condi- 

 tions is, at the most, questionable. They break down in the organ- 

 ism into purine bases and phosphoric acid. 



