t ' 



THE PROTEIN SUBSTANCES. 



do not coincide with the above scheme or do so only with difficulty. 

 At the same time it must be remarked that bodies will be found 

 which seem to rank between the different groups. 



I. Native Albumins. 



The albuminous bodies are never-failing constituents of the 

 animal and vegetable organisms. They are especially found in the 

 animal body, where they form the solid constituents of the muscles, 

 glands, and the blood serum, and they are so generally distributed 

 that there are only a few animal secretions and excretions, such as 

 the tears, perspiration, and perhaps urine, in which they are en- 

 tirely absent or only occur as traces. 



All albuminous bodies contain carbon, hydrogen, nitrogen, oxy- 

 gen, and sulphur; a few contain also phosphorus. Iron is generally 

 found in traces in their ash, and it seems to be a regular constitu- 

 ent of a certain group of the albuminous bodies, namely, the 

 nucleo-albumin group. The composition of the different albu- 

 minous bodies deviates a little, but the variations are within rela- 

 tively close limits. For the better studied animal albuminous 

 bodies the following conposition of the ash-free substance has been 

 given: 



21.50 -- 23.50 " 



A part of the nitrogen of the albumin molecule is loosely com- 

 bined and splits off easily as ammonia by the action of alkalies 

 (NASSE). Sulphur shows the same property in nearly all albu- 

 minous bodies (FLEITMANN, DANILEWSKT, KRUGEE). A part of 

 the sulphur separates as potassium or sodium sulphide on boiling 

 with caustic potash or soda, and may be detected by lead acetate. 

 What remains can only be detected after fusing with nitre and 

 sodium carbonate and testing for sulphates. The albumin molecule 

 therefore contains at least 2 atoms of sulphur. The molecular 



