46 ESSENTIALS OF CHEMICAL PHYSIOLOGY 



contains a high percentage (10-11) of phosphorus. The nuclein 

 obtained from the nuclei or heads of the spermatozoa consists of 

 nucleic acid without any protein admixture. In fishes' spermatozoa, 

 however, there is an exception to this rule, for there it is, as we have 

 already seen, united to pratamine. 



The nucleo-proteins of cell protoplasm are compounds of nucleic 

 acid with a much larger quantity of protein, so that they usually 

 contain only 1 per cent, or less of phosphorus. Some also contain 

 iron, and it is probable that the normal supply of iron to the body is 

 contained in the nucleo-proteins or hcematogens (Bunge) of plant or 

 animal cells. 



Nucleo-proteins may be prepared from cellular structures like 

 thymus, testis, kidney, &c., by two principal methods : 



1. Wooldridges method. The organ is minced and soaked in 

 water for twenty-four hours. Dilute acetic acid added to the aqueous 

 extract precipitates the nucleo-protein. 



2. Sodium chloride method. The minced organ is ground up in a 

 mortar with solid sodium chloride ; the resulting viscous mass is 

 poured into excess of water, and the nucleo-protein rises in strings to 

 the top of the water. 



The solvent usually employed for a nucleo-protein, by whichever 

 method it is prepared, is a 1-per-cent. solution of sodium carbonate. 

 The relationship of nucleo-proteins to the coagulation of the blood is 

 described under that heading. 



Nucleic acid on decomposition yields phosphoric acid, various 

 bases of the xanthine group, and bases also of the pyrimidine group 

 (cytosine, uracil, &c.). In some cases a carbohydrate radical is also 

 obtained ; thus a pentose is obtained from the nucleic acid of the 

 pancreas, the liver, and yeast cells. There appear to be several 

 nucleic acids, which vary in the relative amount they yield of their 

 decomposition products, especially of the members of the xanthine 

 family, which are sometimes called alloxuric, or, more usually, purine 

 bases. The purine bases are closely allied chemically to uric acid, 

 and we shall have to study them again in relation to that substance. 

 The following diagrammatic way of representing the decomposition 

 of nucleo-protein will assist the student in remembering the relation- 

 ships of these substances : 



