350 CHEMISTRY OF THE PROTEIDS 



other animals up till now have been obtained only in an amorphous 

 form. These differences are, however, not sufficient to prove a 

 chemical difference, especially if we take into consideration that the 

 substances in question have by no means been prepared in a pure 

 state. Even amongst the well-known mono- and di-saccharids are seen 

 small differences in general appearance, in the shape of the crystals, or 

 the degree of purity, if the same substance be prepared from different 

 plants, and it requires much trouble and time to purify these sugars 

 to such an extent as to obtain them in a pure state with uniform 

 characteristics. This difficulty becomes very great indeed when we 

 have to deal with the colloidal polysaccharids, for the differences 

 between the starches obtained from potatoes, rice, and maize are very 

 considerable ; but at present it is impossible to tell whether we are 

 dealing with starches differing from one another chemically, or 

 whether the apparent differences are due to the way in which the 

 molecules are arranged in the amylum-granules. 



If the difficulty of preparing pure substances is great amongst the 

 sugars, it is still far greater amongst the albumins, for we have not 

 yet succeeded in preparing pure albumins. The recently discovered 

 precipitin-reaction seemed to be able to throw light on this question 

 of identity or non-identity of the corresponding albumins of different 

 animals, as this reaction permits us to recognise and thereby to dis- 

 tinguish with certainty blood, milk, etc., of different animals. It has, 

 however, already been pointed out that we are not quite certain as to 

 whether the reaction depends at all on albuminous substances. 



At present all the relations are so complicated that we cannot state 

 definitely that the specificity of a species depends on the chemical 

 structure of its albumins. The same holds good for the differences 

 between the albumins of different organs. We know that it is possible 

 to isolate nucleo-albumins, globulins, and probably also myosin-like 

 substances, from the protoplasm of all glandular organs, but we do 

 not know whether these individual chemical substances determine the 

 functions of the organs, or whether the plasm in each case is built up 

 of the same chemical products, but arranged in each individual case in 

 some specific manner. 



There is, however, no doubt that certain older views as to the 

 existence of a special structure characteristic of ' living albumin ' are 

 wrong. The ' unstable (labile) groups of atoms ' are merely ferments 

 or other substances which are contained in the protoplasm, but which for 

 that reason need not be albumins. The view of Kraus 1 and of Umber, 2 



1 Kraus, Deutsche med. Wochensch. 1903, No. 14. 

 2 F. Umber, Berliner Jdin. Wochensch. 1903, No. 39 ; Kraus, ibid. 1904, No. 1. 



