236 



Mr. E. G. Young. 



From qualitative experiments only he claims to have discovered that certain 

 substances, such as glucose, alcohol, lactic acid, urea and acetone, sensitise the 

 serum proteins, while he states that certain German mineral waters protect 

 them. He uses these observations to explain certain pathological conditions, 

 especially old-age cataract. 



When working with solutions of serum albumin which had been several 

 times recrystallised, I had noticed that a marked change was produced in the 

 solution while in glass vessels, so that the protein was almost quantitatively 

 precipitated by mere exposure to sunlight. This precipitation occurred both 

 with material which had been prepared by the alcohol-ether method and that 

 obtained by direct crystallisation from serum, as I have described in a previous 

 communication (6). A heavy precipitate appeared inside of 2 hours which 

 proved soluble only in dilute alkali. The phenomenon seemed of such 

 importance that a more thorough examination of the nature of the chemical 

 reaction underlying it was undertaken. 



As I have been unable to find any record of such a marked change in 

 protein solutions by the action of sunlight in the literature, and further as the 

 reaction was obtained with serum albumin of a purity such as has never, I 

 venture to think, been achieved before, I attributed my observation of light 

 instability to the purity of the preparations. 



The following pages of experimental work are designed to show that the 

 coagulant action of ultra-violet light on albumin in aqueous solution is also 

 brought about by the visible rays of the spectrum when highly purified 

 material is used. Experiments are described which show further that the 

 nature of the reaction is identical with coagulation by heat in all points tested 

 experimentally. That there are two reactions involved is demonstrated and 

 changes in some physical constants of the pure protein solutions by the action 

 of visible light rays are described as evidence towards an explanation of the 

 primary reaction of protein coagulation. 



Methods. 



Dialysis. — For the complete and rapid removal of contaminating electrolytes 

 from solutions of albumin, the dialysing apparatus devised by Sorensen (7) 

 has been used in a slightly modified form. It was necessary that the 

 apparatus should possess the particular advantage of allowing the operator to 

 maintain the solutions at their original concentration or to further concentrate 

 them during dialysis. 



The Preparation of Collodion Membranes. — Medicinal cotton wool was 

 purified by extraction with boiling dilute alkali, followed by repeated changes 

 of boiling water. The cotton was then dried and further extracted in 



