348 CHEMISTRY OF THE PROTEIDS 



This classification into native albumins, dissociation-products, pro- 

 teids, and albuminoids does not include, however, such bodies as the 

 nucleo-albumins. When dealing with these later on, it will be shown 

 that they have nothing whatever to do with the nucleo-proteids, with 

 which they were formerly confounded, and from which they have 

 received their name, except that they contain phosphorus. The 

 nucleo-albumins form a special, physiologically and chemically well- 

 defined class ; it is immaterial whether we regard them as proteids or 

 as phosphorus -containing albumins. The same holds good of the 

 mucins and allied substances, which may be classified as albumins 

 with a specially high amount of carbohydrate, or as glyco-proteids. 

 Following Hammarsten, the nucleo-albumins have been described under 

 the albumins, while the mucins and mucoids are counted amongst the 

 proteids. It is best to drop the expression ' nucleo-albumin ' alto- 

 gether, as these substances have nothing to do with the nucleus, 

 and to use instead the term " phospho-globulin," proposed by Cohnheim. 



The former classification of native albumins into the water-soluble 

 albumins and into the water-insoluble globulins, which latter are, how- 

 ever, soluble in acids, alkalies, and salts, seems to have received a certain 

 amount of justification through more recent work. Although albumins 

 differ greatly in their composition, they resemble one another in 

 possessing the power of crystallising ; the globulins also agree well 

 with one another as far as salting-out is concerned. The group of 

 coagulable albumins is certainly not a homogeneous one, and has 

 therefore been subdivided. The important reserve-albumins of seeds, 

 which sometimes go under the name of vitellines, and at other times 

 are called globulins, have been classed as a special group. 



Between the individual groups of the scheme shown below there 

 are transition forms which it is sometimes very difficult to class. 

 Many albumins have been examined not as such, but in the form of 

 their salts, a factor which must never be lost sight of when dealing 

 with their solubilities. 



I. Albumins proper 



1. Albumins: serum-albumin, egg-albumin, 1 lac t-albumin. 



2. Globulins: serum -globulin, egg-globulin, lacto- globulin, cell- 



globulins. 



3. Plant-globulins and -vitellines. 



4. Fibrinogen. 



5. Myosin and allied substances. 



6. Phosphorus -containing albumins (nucleo-albumins), caseins, 



1 The author does not consider egg-albumin to be a typical albumin, see p. 352. 



