132 BIO-CHEMICAL JOURNAL 



filter the filter paper containing small quantities of the coagulum is 

 transferred to the Kjchldahl flask. Sulphuric acid is then added, the 

 mixture incinerated and the nitrogen determined in the usual way. 



In the experiments with serum described in Part III, 15 c.c. were 

 always used for each experiment. The total nitrogen was estimated in 

 this quantity by incinerating with 30 c.c. concentrated sulphuric acid ; 

 a filter paper was added to the mixture, so that the total coagulable 

 albumen nitrogen was always determined under the same conditions. 

 Another 15 c.c. were used for the determination of the coagulable 

 nitrogen in the way just described. 



For the examination of the tissues 5 grams of material were used 

 for each determination. The finely divided tissue was weighed on a 

 photographic balance (accurate to about cro2 of a gram). It was^then 

 transferred to a flat-bottomed porcelain dish with a knife, and mixed 

 up by means of the knife with a little more than an equal weight of 

 the sulphate of soda. The glass pan of the balance was carefully 

 cleansed by rubbing up with fresh quantities of sulphate of soda, and 

 the mixture kept until wanted. The mixture was then powdered in a 

 mortar, coagulated with alcohol, washed, and the nitrogen of the 

 coagulum determined in the way already described for serum. The 

 total nitrogen was determined in 5 grams of fresh tissue. Thirty c.c. 

 concentrated sulphuric acid were employed for incineration in each case. 

 A filter paper was added in the determination of the total nitrogen as 

 in the case of the serum. 



When working with solutions of albumens the same method can 

 be employed. A little more sulphate of soda is added than the weight 

 of water present. 



The following series of experiments illustrate the foregoing re- 

 marks. In the last series the coagulable albumen is determined in a 

 serum ; the same serum is mixed with a concentrated solution of Witte's 

 peptone, and the coagulable albumen determined in the mixture. 

 These experiments were carried out very rapidly, and although the 

 coagulum was washed only twice by decantation, it will be observed 

 that only a minute quantity of the peptone nitrogen has been carried 

 down. Far larger quantities of water-soluble bodies were present in 

 this case than are ever met with in tissues. 



