76 MASS. EXPERIMENT STATION BULLETIN 378 



methods available and also a yeast fermentation method. Yeast cells 

 require thiamin in order to grow and cause sugar to ferment. The latter 

 method is suitable for the determination of thiamin in urine and is the 

 one we are using. 



The subjects who participate in this study will be contributing both 

 to scientific knowledge and to their own well-being, we hope. Each sub- 

 ject will be expected to submit to a complete physical examination by 

 a cooperating physician. Subjects will not be expected to alter their usual 

 food habits or disrupt their daily routine in any way. They will be asked 

 to keep a record and furnish us with a list of foods eaten for a week or 

 more preceding and during certain tests. Any medicines, laxatives, vita- 

 min supplements, etc., will need to be recorded. Subjects will be asked 

 to collect accurate 24-hour urine specimens. The plan of the experiment 

 will be to study first the usual amount of thiamin excreted by each subject 

 on his habitual diet without vitamin supplement of any kind. After this 

 preliminary study, carefully graded doses of thiamin will be prescribed. 



This project was started in the fall of 1940 and is being sponsored par- 

 tially by Standard Brands Incorporated. 



Cause and Control of Nutritional Cataract. (H. S. Mitchell, G. M. Cook 

 and A. W. Wertz.) The experimental production of cataract in rats by 

 feeding rations containing galactose has become a means of studjang the 

 effect of other dietary factors upon the lens. The susceptibility of this 

 delicate tissue to injury from foreign substances as galactose in the blood 

 stream is materially reduced by a liberal amount of protein in the ration. 

 Whether protein or some nitrogenous substance might be protective 

 against lenticular injury due to other causes than galactose is not known. 

 The nature of the protein or of the protein constituents which might 

 exert this protective action have been the subject of further study, and 

 reports have been published as follows: 



1. The Aiiti-Cataractogcjiic Action of Certain Nitrogounis Factors. (H. 

 S. Mitchell, G. M. Cook, and M. D. Henderson. Arch. Ophth. 24, 990-98, 

 1940.) Data presented in this paper confirm earlier reports that inade- 

 quate protein (5 percent) aggravates and that high protein (45 percent) 

 inhibits the development of cataract in rats fed galactose. Attention was 

 then turned to the investigation of certain nitrogenous factors. An en- 

 zymic hydrolysate of casein gave the same degree of protection as its 

 nitrogen equivalent in commercial casein. Cystine (2 percent) and 

 methionine (2 percent) gave only slight or irregular protection. More- 

 over, when the sulfhydryl amino acids were made less available by the 

 addition of 100 mg. of iodoacetic acid or 250 mg. naphthalene to 100 g. 

 of ration, growth was retarded but cataractous changes were not hastened. 

 Urea at 1, 5, and 10 percent levels gave less protection than an equivalent 

 of N fed as protein. Choline was studied by adding 1, 2, 4, and 8 percent 

 to a 5 percent casein ration. Growth was progressively poorer the higher 

 the level of choline fed and there was no protection against cataract. 



2. The Effect of Dry Heat Upon the Anti-Cataractogenic Quality of Cer- 

 tain Proteins. (M. D. Henderson and H. S. Mitchell. J. Nutri. 21, Feb. 1941.) 

 The knowledge that protein exerts protective action against galactose 

 injury in rats, raises the question as to whether the type of treatment 

 which is known to decrease the growth value of a protein will also afifect 

 its cataract-inhibiting quality. Tlie four proteins — casein, egg albumin, 

 wheat gluten, and beef fibrin — were fed as purchased and after being 



