Power of Crystalline Ovalbumin and Serum Albumin. 



33 



however, must be minute, since concentrations of over 5 per cent, of 

 albumin can be examined in 200 mm. polarimeter tubes with ease. The 

 work of Palmer and Eckles (1914) tends to show that the pigments are 

 carotin and xanthophyll of plant tissues. But since carotin, which pre- 

 dominates greatly in horse serum, has such an intense colouring power, the 

 amount in the solution used optically must be very small — less than 1 mgrm. 

 in 100 c.c. 



The true relationship between the fatty material or pigment and the protein 

 in natural serum is best understood, to my mind, by the concept that in such 

 complex compounds as the proteins there is no sharp distinction between the 

 so-called physical adsorption and chemical union of associated substances. As 

 Langmuir has pointed out from inorganic studies adsorption is fundamentally 

 chemical. 



The Insoluble Residue. 



I have examined the residues which remained after the first crystallisation 

 of several lots of albumin from serum. It is very obvious that they differ 

 markedly in texture. Occasionally they can be collected with difficulty on 

 account of being an oil. As such it is impossible to centrifuge and difficult to 

 filter. When separated it is found to be entirely and readily soluble in ether, 

 except for a little contaminating protein. This solution shows a very heavy 

 precipitate on adding acetone but an oil is deposited on slow concentration. 

 At other times the residue is a solid which can be readily centrifuged off and 

 washed free from pigment. I have dissolved this in ether and hot alcohol. 

 On cooling the solution in alcohol deposits, needles of the appearance of chole- 

 sterol esters and the solutions give a very strong cholesterol reaction. 



Since no amorphous material is ever visible under the highest power of the 

 compound microscope when the first crystalline product is examined, yet a 

 very marked residue remains on attempting resolution, I examined the 

 crystals while they were going into solution under the microscope. It then 

 became clear why the albumin dissolved so slowly. As the highly refractive 

 protein interior of the crystal disappeared there still remained the outline of 

 the crystal. Soon the field became covered with these shells of the former 

 crystals without any remaining protein. There was still no amorphous 

 material. On agitating the slide, however, the crystal outlines rounded into 

 fat-like globules. It would thus appear that each crystal had had a thin 

 covering of fatty material deposited about it. This would naturally interfere 

 with the process of crystallisation and make the crystal sizes vary. It is 

 noticeable that large crystals are first formed which are four or five times the 

 mass of smaller ones appearing later. Furthermore the presence of this fat- 

 like material alters the shape of the crystal, obliterating angles and inhibiting 



VOL. XCIII. — B. D 



