SOAPS, PROTEIN DERIVATIVES AND TISSUES 209 



precipitation, irreversible " coagulation," etc. A detailed con- 

 sideration of many proteins is impossible within the pages of this 

 volume, but the two to be discussed may serve to illustrate the 

 main types. For purposes of illustration we shall take up, in 

 analogy to the similar types of pure fatty acids, (a) a protein 

 which is " insoluble " in water, namely, egg-globulin and (6) 

 another which is " soluble," namely, gelatin. What is said of 

 egg-globulin may be taken to apply to all the globulins, casein, 

 myosin and nucleic acid. What is said of gelatin may be applied 

 to the various albumins. 1 



3. The System Egg-Globulin /Water 



The " neutral " globulin used in the experiments about to 

 be described was obtained by diluting strongly with distilled water 

 (8 volumes) the whites of absolutely fresh eggs. The globulin 

 which fell out at the end of twenty-four hours in an ice box was 

 simply filtered off, washed several times with distilled water and 

 used at once in its moist condition. While by more elaborate 

 methods a " chemically " purer product might have been obtained, 

 we feared the consequences of the more drastic chemical methods 

 necessary to produce such upon the colloid properties of the 

 final product. The globulin employed in the following experi- 

 ments was all from the same lot, contained 92 percent water 

 as used and 0.045 percent ash calculated upon the wet weight 

 of the globulin. 



Moist globulin (in analogy to the higher fatty acids) is obvi- 

 ously " insoluble " in water and as con ipa KM 1 with gelatin, albumin, 

 etc.. a relatively poor solvent for water (92 percent). We wished, 

 first, to show that a soap-like compound (a basic globulinate) 

 could be obtained from such globulin through treat mcnt with 

 a proper alkali, which, in the presence of the right amount of water 

 would (like the corresponding soap) yield a solid jelly, in other 



1 The purest gelatins <>n which tin- ordinary colloid-chemical studies have 

 been made, to which we refer here und ujxm which some MOOMding e\|>eri- 

 mentB are based (see page 218) still contain traces of salts. WOLFGANG 

 OarwALD has directed my attention to the fact that when such gelatins are 

 subjected to dialysis while ;iu electric current is pa--eo! through them a uelatm 

 free from all base and acid may be obtained. Such gelatin i-. h.., 



iMe" in water and as little hydnttahle as the ordinary globulins. 

 Obviously, under -udi circumstance-, the u-havior of nil the proteins (includ- 

 ing in other words gelatin and the "albumins") becomes that of the type 

 described un-l- r the globulins. 



