amounts, with the exception of vitamin B which was lacking. 
It had the following composition: . 
Diet 94 
per cent. 
Casein 18 
Butter fat - 10 
Starch 68 
Salt mixture (Osborne and Mendel) *° 4 
Later, merely as a factor of safety, cod liver oil was substi- 
tuted for one-fifth of the butter fat, making diet 107. The in- 
gredients of the diet were weighed out and intimately mixed 
first by hand and then transferred to a mechanical mixer and 
stirred for five minutes. 
The casein was prepared from the commercial product 
by purification in the manner suggested by Sherman and Husa 
(unpublished experiments) as follows: One liter of 60 per 
cent. alcohol (by weight) was added to 200 grams of casein 
and the mixture stirred for one-half hour by means of a 
mechanical stirrer and was then allowed-to stand for five and 
one-half hours. After this period the casein was filtered off 
through a Buchner funnel and washed once in the funnel 
‘with 500 cc. of 60 per cent. alcohol. The casein was again 
treated with one liter of 60 per cent. alcohol as before but this 
time was left to stand for eighteen hours. It was filtered off 
and washed as before with 500 cc. of 60 per cent. alcohol and 
finally with 500 cc. of 90 per cent. alcohol. The last washing 
merely facilitates the drying. The casein was removed from 
the filter and spread out in a thin layer and allowed to become 
air-dry. Throughout this paper the strength of alcohol used 
is always given in per cent. by weight. — 
The butter was melted at a temperature not exceeding 
45° C. All the curd, salt and water settles to the bottom of 
the vessel and may be easily removed when the butter solidi- 
fies. The butter fat is again melted at a low temperature, and 
filtered through filter paper using a hot water funnel. 
The salt mixture described by Osborne and Mendel * 
was used. Commercially pure corn starch, which according 
8 
