52 PHYSIOLOGICAL CHEMISTRY. 



acetate, and the new filtrate is treated with sulphuretted hydrogen 

 to remove the lead, again filtered, concentrated, and, after adding 

 an excess of ammonia, precipitated with silver nitrate. The silver 

 combination (with the addition of some urea to prevent nitrification) 

 is dissolved in not too large a quantity of boiling nitric acid of sp. 

 gr. 1.1, and this solution filtered boiling hot. On cooling the silver 

 xanthin remains in the solution, while the double combination of 

 guanin, hypoxanthin, and adenin crystallizes. The xanthin silver 

 may be removed from the filtrate by the addition of ammonia, and 

 the xanthin set free by means of sulphuretted hydrogen. The 

 three above-mentioned silver nitrate combinations are decomposed 

 in water with ammonium sulphide and heat; the silver sulphide is 

 filtered, the filtrate concentrated, saturated with ammonia, and 

 digested on the water-bath. The guanin remains undissolved,. 

 while the other two bases pass into solution. A part of the guanin 

 is still retained by the silver sulphide, and may be liberated by 

 boiling it with dilute hydrochloric acid and then saturating the 

 filtrate with ammonia. When the above filtrate, containing the 

 adenin and hypoxanthin, which has been, if necessary, freed 

 from ammonia by evaporation, is allowed to cool, the adenin 

 separates, while the hypoxanthin remains in solution. The chief 

 points in the above method are used for the quantitative esti- 

 mation of the xanthin bodies. If the solution of adenin and 

 hypoxanthin is evaporated to dryness, the residue weighed, and the 

 amount of nitrogen determined, from this determination and from 

 the amount of nitrogen in hypoxanthin (41.17$) and in adenin 

 (51.87$) the quantity of each of these bodies may be calculated. 



In the generative animal cells, and especially in those which 

 develop embryonic tissue, CL. BERNARD and HENSEK have dis- 

 covered a carbohydrate, the glycogen. According to HOPPE- 

 SEYLER it seems to be a never-failing constituent of the cells as 

 soon as they show embryonic movements, and he found this carbo- 

 hydrate in the white blood-corpuscles but not in the developed 

 motionless pus-corpuscles. The relationship which exists between 

 the consumption of glycogen and muscular work (see Chapter IX) 

 leads us to suppose that such a consumption takes place in the 

 movements of the animal protoplasm. On the other side the 

 widely-diffused occurrence of glycogen in embryonic tissues, as 

 also its occurrence in pathological swellings and in abundant cell- 

 formations, seems of the greatest importance in the formation and 

 development of the cell. 



In grown animals the glycogen is found in the muscles and 



