254 
Journal o f Agricultural Research 
Vol. XXIX, No. 5 
Shipley, and Cramer ( 2 ) obtained 
similar results. Hess states that a 
smaller quantity than 0.25 gm. of 
egg yolk would probably have been 
sufficient; but no attempt was made to 
force the feeding to a minimum. 
EXPERIMENTAL 
COMPOSITION AND PREPARATION OF DIET 
The experiments described in this 
paper were undertaken to ascertain, as 
nearly as present methods permit, the 
smallest quantity of fresh whole egg 
which will cure rats of xerophthalmia, 
and enable them to grow at a normal 
rate. 
The eggs used were laid during the 
summer months, and were from hens 
that had access to plenty of fresh, 
green food. 
Young albino rats weighing from 45 to 
55 gm. were placed on a basal ration 
found experimentally to be practically 
free from vitamin A, which had the 
following composition: Casein, 15 per 
cent; corn starch, 65 per cent; Crisco, 
15 per cent; salt mixture, 5 per cent. 
Rats on this diet usually developed 
xerophthalmia in 40 to 50 days. 
Vitamin B was supplied by 0.2 gm. of 
a commercial autolysed yeast prepara¬ 
tion (marmite) fed separately each day. 
The casein was prepared by pre¬ 
cipitation at its isoelectric point from 
fresh skimmed milk, and purified by 
dissolving it in dilute sodium hydroxide 
and reprecipitating with acetic acid. 
This treatment was followed by extrac¬ 
tion with alcohol and ether. The 
casein was then dried at 110° C. The 
starch was not specially treated, since 
it was not found to contain a detect¬ 
able quantity of vitamin. Air was 
bubbled through the Crisco at about 
100° for 48 hours, to insure the de¬ 
struction of any vitamin which may 
have been present. The salt mixture 
used was that described by Osborne and 
Mendel ( 8 ). The egg was thoroughly 
beaten to a homogeneous consistency, 
and fed daily together with the mar¬ 
mite, separate from the rest of the diet. 
POTENCIES OF VARIOUS QUANTITIES OF 
THE WHOLE FRESH EGG FOR THE 
PROMOTION OF GROWTH AND CURING 
OF XERPHTHALMIA 
No curative dosage of egg was given 
until the rats had developed definite 
xerophthalmia. On a vitamin A free 
basal diet young rats usually make an 
initial growth at a fair rate for a few 
weeks and then cease to grow or begin 
to declineTin weight. Many investi¬ 
gators begin to feed the material to be 
«ested at this point, and note the effect 
on the growth of the animals as an 
indication of the vitamin potency of 
the material. Sometimes the first 
decline in weight is but temporary, and 
growth for a short period again follows, 
even without the addition of any 
vitamins. But waiting until xeroph¬ 
thalmia is evident before giving the 
substance to be tested may not only 
prevent a possible error due to this 
phenomenon, but permits a study of 
the effect of the vitamin A both as an 
antixerophthalmic and as a growth- 
promoting factor. These functions 
may be distinct and not strictly 
parallel. 
The first trials were made with 0.5 
gm. of egg given daily after the onset 
of xerophthalmia. The results are 
shown in Figure 1. As can be seen, the 
feeding of the egg promptly arrested 
the decline in weight, and enabled the 
rats to grow at a very fair, although 
not normal, rate. Xerophthalmia, which 
was very severe in the case of rats No. 
1783 and No. 1785, was entirely cured 
in from 10 to 25 days and at the close 
of the experiment all the rats were in 
very good condition. 
After it was found that 0.5 gm. of 
egg daily would cure xerophthalmia, 
without, however, permitting normal 
subsequent growth, several rats were 
fed 0.75 gm. of egg (fig. 2). The re¬ 
sponse to this was prompt. Rat No. 
1794 developed an abnormality of 
tooth growth which interfered with 
feeding, and after an initial period of 
rapid gain had to be removed from the 
diet. Rat No. 1857, after having been 
given the egg, grew at a rate far exceed¬ 
ing normal. The eyes of all cleared up 
within a week. 
It is evident that 0.75 gm. daily of 
fresh egg was sufficient to bring about 
normal growth in rats which had de¬ 
clined in weight and had developed 
xerophthalmia as a result of a lack of 
vitamin A in the diet. Growth at a 
rate of only about twp-thirds of normal 
was secured on 0.5 gm. of egg. The 
minimum quantity of egg required to 
admit of normal growth can not, how¬ 
ever, be safely decided from these 
experiments, since the rats were suffer¬ 
ing badly from avitaminosis when the 
egg feeding was started. Consequently, 
more egg might have been necessary to 
permit subsequent growth at a normal 
rate than would have been the case had 
they received the egg from the begin¬ 
ning of the experiment. In another 
series of experiments in which 0.5 gm. 
of egg was fed daily from the beginning 
to young rats weighing about 50 gm.. 
growth at the normal rate was secured 
for about 100 days, after which the 
growth became subnormal. From 
