144 COLLOIDS IN BIOLOGY. AND MEDICINE 



Though native albumins are usually hydrophile, they become hydro- 

 phobe upon heat coagulation. Traced of acids and salts cause precipita- 

 tion. The precipitate of albumin induced by freezing is irreversible. 



Albumin may be partly changed to globulins, and ultimately 

 coagulated and precipitated by light, particularly light of short wave 

 length (G. DREYER and HAUSEN, CHALUPECKY), ultraviolet rays are 

 particularly intense in their action (Bo VIE). This is especially 

 significant for some future explanation of the action of sunlight on the 

 organism. SCHANZ attributes to it the clouding of the crystalline 

 lens in cataract. The rays of shortest wave length, the Roentgen 

 rays, coagulate albumin. 



A number of proteins have been crystallized (e.g., egg albumin, 

 horse serum albumin, hemoglobin, aleuron) and though the shape 

 of the crystal is characteristic for the kind of albumin, nevertheless 

 it is impossible to obtain the crystals absolutely chemically pure as in 

 the case of crystalloids (see p. 71). 



Albumin solutions have been studied ultramicroscopically by E. 



RAHLMANN,* 2 E. VON BEHRING, H. MUCH, RoMER and C. SlEBERT,* 



by L. MiCHAELis,* 1 L. PINKUSSOHN* and J. LEMANISSIER.* The 

 results expected at the outset were not realized, so that, in recent 

 years, there has been little heard on the subject. In my opinion 

 this is unfortunate; I am inclined to believe that valuable data 

 might be gleaned from a properly controlled ultramicroscopic study 

 of proteins. It is evident that a large part of albumin solutions is 

 amicroscopic, so that only such portions are seen as show a different 

 refraction than water or physiological salt solution. An albuminous 

 solution shows a different number of ultramicrons, entirely depend- 

 ing upon whether it has been prepared in water or in physiological 

 salt solution (MICHAELIS); and with different dilutions depending 

 upon the salt content, a different number of small particles become 

 visible (RAHLMANN). On this account L. MICHAELIS and J. LEMA- 

 NISSIER do not share the opinion of E. RAHLMANN and the school of 

 E. VON BEHRING as to the suitability of ultramicroscopic observa- 

 tion for the quantitative determination of albumin, e.g., in the urine. 

 Great interest must attach to ultramicroscopic observations of the 

 cleavage of albumin by pepsin, 1 the influence of therapeutically 

 active substances (ferric chlorid, alum, tannic acid, silver nitrate, 

 copper sulphate, collargol, etc.), as well as the effect of dyes on solu- 

 tion of albumin (RAHLMANN). A few submicrons were found by J. 

 LEMANISSIER in albumin solution and many in hemoglobin, but they 

 disappeared in 24 hours. 



Ultrafiltration of albumin solution is still in its infancy. H. 

 BECHHOLD has shown that the particles of serum albumin are some- 



1 [Already observed by J. ALEXANDER. Jour. Am. Chem. Soc., Vol. XXXII, 

 p. 680, et scq. Tr.] 



