E. V. MeCollum and N. Simmonds 83 
The Solubility of the Water-Soluble B as It Exists in Animal 
Tissues. 
In our studies of the fat-soluble A we have repeatedly ob- 
served that, while ether extracts of egg yolk and the ether-soluble 
constituents of milk contain the unidentified A, plant fats, iso- 
lated from the seed by means of ether apparently never contain 
this substance (18). It remains after exhaustive extraction, in 
the fat-free residue of the plant tissue. We have suggested that 
the substance (fat-soluble A) is in chemical union in the plant 
tissues in a form which is not soluble in ether, and that during 
digestion or absorption it is set free and, being readily soluble in 
fats (18), thereafter accompanies the fats in the animal body. 
It seemed desirable to extend our observations on the solubility 
of the water-soluble dietary essential in organic solvents to an 
animal tissue, since one cannot extend with confidence the re- 
sults obtained with plant tissues to tissues of animal origin, 
owing to the possibility that it exists in the animal cell in chemical 
union. Our data on this subject is still meager but that obtained 
with dried, unheated pig kidney will be reported here. 
Chart 11. Lots 962 A, 961 A, 961 B, and 960 B. 
Lot 962 A. Period 1.—Ration: Purified food mixture plus 5 per cent of 
butter fat. 
Period 2.—Ration: Same as Period 1 with the addition of 6 per cent of 
dry, uncooked pig kidney extracted with ether and then with benzene. 
This experiment is in agreement with Lot 961 A, which shows 
that the physiologically active substance is not extracted to an 
appreciable extent from animal tissue (kidney) by ether or 
benzene. ) 
Lot 961 A. Period 1—Ration: Purified food mixture plus 5 per cent of 
butter fat. 
Period 2.—Ration: Same as Period 1, but with the benzene extract of 
ether-extracted pig kidney equivalent to 6 gm. of tissue per 100 gm. of 
ration. 
Period 3.—Ration: Same as Period 1, but with the addition of the ben- 
zene extract of the alcoholic extract of ether-extracted raw navy beans 
equivalent to 30 gm. of beans per 100 gm. of ration (the ration of Chart 1, 
Lot 953 A, Period 3). 
The preparation from beans was introduced in Period 3 to demonstrate 
the capacity of the enimals to grow. 
