310 PRACTICAL PHYSIOLOGY 



This brown sediment can be further decomposed into nucleic acid and 

 protein by dissolving it in alkali and adding 0*3 % hydrochloric acid in 

 alcohol. This precipitates the nucleic acid. If this be collected and 

 heated in a sealed tube with hydrochloric acid, it splits into a number 

 of simpler bodies. Guanylic acid, the simplest nucleic acid found in 

 the pancreas, yields phosphoric acid, guanine, and pentose. Other 

 nucleic acids which occur with the guanylic acid yield phosphoric acid, 

 guanine, and adenine, laevulinic acid (probably from decomposition of 

 a hexose), the pyrimidine base cytosine, and probably other pyrimidine 

 bases. 



SCHEMA OF RELATIONSHIP OF NUCLEIN, ETC. 



Nucleo-protein 

 (digested with pepsin) 



Nuclein (precipitated as a brown sediment, Peptone 



decomposed l>y acid alcohol) (goes into solution) 



Acid Meta-protein (in solution) Nucleic Acid (white precipitate) 



heated in closed tube with HC1 



! 



Purin bodies Carbohydrate Phosphoric Acid Pyrimidine bases 



(adenin, guanin) (hexose or pentose) Cytosin 



The presence of phosphorus in nucleo-protein may be demonstrated 

 by heating it with combustion mixture (cf. phospho-protein). Its phos- 

 phoric acid, however, is not split off by incubation with 1 % NaOH 

 at 37C. for 24 hours; nor are nucleo-proteins clotted by the rennet 

 enzyme. 



We come lastly to the products of protein hydrolysis, which will 

 be dealt with more fully under Digestion. When albumin is subjected 

 to the action of a weak acid or weak alkali it is transformed into a 

 derived protein or meta-protein. These closely resemble the globulins. 



Acid and Alkali Meta-protein. 



EXPERIMENT XIII. To some diluted egg-white add two or three 

 drops of 10 % HC1. Place in water bath at body temperature for 

 five minutes. Acid meta-protein is formed. 



Note. (a) That no coagulum now appears on heating. 



(b) It is precipitated by making the solution neutral or very 



faintly alkaline. 



(c) It is salted out by half saturation with ammonium sulphate 



(like a globulin). 



(d) If neutralised and suspended in water it is coagulated on boiling. 



