ALBUMINOUS BODIES. 59 



Group II. ALBUMINOUS BODIES. 



It is difficult to say how far these bodies exist as such in the 

 living organism, but they can be obtained from nearly all parts, 

 particularly those which contain active protoplasm, and after its 

 death they can be detected in abundance. As may be seen, by 

 testing for their presence in living protoplasm, the addition of any 

 chemical reagent or treatment causes its death, so that although 

 albumins appear in the test-tube, this cannot be accepted as proof 

 that they would have answered to the tests before the protoplasm 

 was changed by its death. 



They do not occur normally in any secretion except those sub- 

 stances which tend to nourish the adult body, and to form and 

 nourish the offspring, viz., the ovum, semen, and milk. No satis- 

 factory formula has been suggested to express their chemical com- 

 position, but the average percentage of the elements they contain 

 is remarkably alike in all members of the group. This may be 

 said to be in round numbers as follows : 



Oxygen, '. . 21 per cent. 



Hydrogen, 7 " 



Nitrogen, 16 " 



Carbon, 53 



Sulphur, 1 



They are amorphous, of varying solubility, and with one excep- 

 tion indiffusible in water. 



As far as we know at present, albumins cannot be constructed 

 de novo in the animal body, but must be supplied in one form or 

 another as part of the food. Albumins are therefore always the 

 outcome of the activity of vegetable life. 



They can be recognized by the following tests : 



1. Strong nitric acid gives a pale yellow color to strong solu- 



tions or solid albumin, which turns to deep orange when 

 ammonia is added (Xanthoproteic test). 



2. Millon's Reagent (acid solution of proto-nitrate of mercury) 



gives a white precipitate which soon turns yellow, 



