ADVANCED PHYSIOLOGICAL CHEMISTEY 



433 



of these. 1 Thus, the nucleic acid obtained from the thymus yields 

 mainly adenin, whereas that obtained from the pancreas almost entirely 

 guanin. Besides these alloxuric bodies, other decomposition products 

 have been obtained, such as a body called Thymin, so called because it 

 was first obtained from the thymus nucleic acid. It has since been 

 obtained from several other varieties of nucleic acid. 



Several nucleic acids also contain a carbohydrate in their molecule, 

 thus pancreatic nucleic acid yields a pentose, and yeast nucleic acid a 

 hexose and a pentose. On the other hand, thymus nucleic acid does 

 not yield any carbohydrate. 



CHAPTER IV. 



FATS AND ALLIED BODIES. 



Method of Extracting an Organ or Tissue with Ether. The simplest 

 method is by means of Soxhlet's apparatus (Fig. 269). This consists of 

 an extracting chamber into which opens, near the top, a side tube, 

 connected below with a flask, in which is placed the ether. This 

 flask is placed on a water bath, and the ether passes 

 into the chamber, and then into a Liebig's condenser, 

 where it is condensed and trickles back into the ex- 

 tracting chamber, in which it gradually accumulates till 

 it reaches the level of the bend in the side tube when 

 syphon action is established, and the whole of the 

 ether drains into the distilling flask. The tissue or 

 organ to be extracted is placed in the extracting 

 chamber, being wrapped up in a piece of filter paper. 

 The lukewarm condensed ether as it accumulates in 

 the chamber dissolves out the fat, and carries it into 

 the distilling flask. The process should be allowed 

 to proceed for several hours. The contents of the 

 distilling flask are then removed to a flat dish, and 

 the ether allowed to evaporate. 



Method for Separating Neutral Fat and Fatty 

 Acid. Fatty acid combines with sodium carbonate to form a soap, 

 whereas neutral fat does not. In order to separate the one from 



1 More usually, however, they are named according to the organ from which 

 they are separated. 



2E 



FIG. 2(59. Soxhlet's 

 apparatus. 



