CH. XXV1I1.] THE CONJUGATED PROTEINS 431 



spermatozoa, however, there is an exception to this rule, for there it 

 is, as we have already seen, united to protamine. 



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 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 such as thymus, 

 testis, kidney, etc. , 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, whichever method it is 

 prepared by, 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 yields, among its decomposition products, phosphoric 

 acid, various bases of the purine group, and bases also of the 

 pyrimidine group. A carbohydrate radical is also obtained. The 

 following diagrammatic way of representing the decomposition of 

 nucleo-protein puts the matter more clearly : 



NUCLEO-PROTEIN 

 subjected to gastric digestion yields 



I I 



Protein converted into peptone, Nuclein, which remains as an insoluble 



which goes into solution. residue. If this is dissolved in alkali 



and hydrochloric acid added, it yields 



Protein converted into acid A precipitate consisting of nucleic 



meta-protein in solution. acid. If this is heated in a sealed 



tube with hydrochloric acid, it yields 



Phosphoric acid. Carbohydrate. Purine bases. Pyrimidine bases. 



Kecent research on the nucleic acids obtained from various 

 mammalian organs indicates that they fall into two main classes : 

 (1) Nucleic acid proper. This yields on decomposition 



(a) Phosphoric acid. 



(b) A sugar, which is a hexose, but has not yet been 



identified further ; Levene has found that in the nucleic 

 acids of vegetable origin (fqr instance from yeast) the 

 sugar present is a pentose (d-ribose). 



(c) Two members of the purine group in the same proportion 



namely, adenine and guanine. 



