SPECIAL REACTIONS OF THE ALBUMINS. 43 



of the form in which the so-called oxidized sulphur existed. 

 Morner has shown that in certain albumins the cystin-yielding 

 complex comprises not only the loosely combined, but also a por- 

 tion at least of the firmly united variety. In the case of the kera- 

 tins of horn and hair it seems quite likely indeed that the sulphur 

 is present only in this form. The shells of birds' eggs, on the 

 other hand, if they represent a chemical unity at all, contain sev- 

 eral sulphur atoms, which are present in at least two forms, and 

 only one of which appears to be represented by the cystin-yielding 

 group ; this portion corresponds to three-quarters of the total 

 sulphur, while one-quarter is present in some other form. But 

 even here the cystin sulphur includes a certain portion of the firmly 

 combined sulphur. The same is true of serum-globulin, while in 

 fibrinogcn and ovalbumin at least one other sulphur complex 

 appears to exist in addition to the one which is obtained on hydroly- 

 sis as cystin. The latter in the case of fibrinogen represents one-half 

 of the total sulphur, and in the case of ovalbumin only one- third, 

 while the remaining two-thirds exist in a yet unknown form ; one- 

 third of this in turn may under certain circumstances escape in 

 volatile form, which, however, is not hydrogen sulphide. 



In the albuminous molecule the disulphide cystin is the primary 

 radicle, and not cystem ; it hence contains at least two molecules of 

 sulphur. Of other sulphur compounds which have been obtained 

 from the albumins, there may be mentioned thiolactic acid, thiogly- 

 colic acid, ethyl sulphide, and ethyl- and methyl-merkaptan. To 

 what extent these bodies occur as radicles in the albuminous mole- 

 cule is an open question. In the case of those albumins in which 

 the sulphur is only present in the cystin form they could only be 

 secondary, but in the albumins which contain more than one 

 sulphur group some of them at least might occur preformed. 



Oxidized sulphur viz., sulphur combined with oxygen does 

 not occur in the albumins. 



The amount of sulphur differs in the different albumins, as seen 

 in the following table (see also table on p. 46) : 



Total sulphur Loosely combined 



(per cent.). sulphur (per cent.). 



Serum-albumin 1.73 l 1.29 



Serum-globulin 0.97 l 0.67 



Fibrinogen 1.07 l 0.46 



Egg-albumin 1.58 * 0.43 



Haemoglobin 0.43 0.19 



Globin 0.42 0.20 



Casein 0.70 very little. 



Keratin (from horn) 3.23 l 2.48 



Keratin (from egg-shells) 4.19 2.47 



Keratin (from human hair) 5.43 l 4.07 



The Carbohydrate Group. To judge from recent researches a car- 

 bohydrate group is present with few exceptions in all albumins. It 

 1 After deducting sulphur present as SO 3 . 



