132 
Journal of Agricultural Research 
Vol. XIV, No. 3 
which were carried on with the bodies of baby chicks and of i^-pound 
broilers be studied, it will be noted that there is a material increase of 
the greater essential inorganic constituents of the bone—namely, cal¬ 
cium, magnesium, and phosphorus. The baby chick is provided with 
down. This is gradually replaced with a coat of feathers as the chick 
develops, which calls for an increase of sulphur. It will also be noted 
that in this element there has been a material increase. To carry our com¬ 
parative study a step farther, it will be noted that, as the bird develops 
to maturity, there is a still greater increase in calcium, magnesium, phos¬ 
phorus, and sulphur, though the iron content is only slightly increased. 
The bird has no sweat glands and only one oil gland, the latter a double 
lobulated tubular gland located dorsally at the base of the tail. This 
gland furnishes oil for the bird to distribute to each feather by the aid 
of its beak. The excretions of the body of the fowl are cast off by way 
of the lungs, kidneys, and intestinal tract. The ureters, large intestine, 
oviduct, and vasa deferentia all empty into a reservoir, an expansion of 
the terminal end of the gut, called the “cloaca,” which in turn empties 
through the anus to the external world. This arrangement makes the 
isolation of elements eliminated by the kidneys a difficult task; in fact, 
it is impossible except through surgical interference, and this has many 
difficulties. In these particular experiments we have not attempted this. 
In an average of two lots in this series of experiments the following 
quantities of feeds were required to produce i gm. of gain in weight: 
Milk, 7.49 gm.; mash and grain mixtures, 2.91 gm.; green feed, 1 gm.; 
total 11.44 gm. In these cases the feed was kept constantly before the 
flocks, so that the consumption was a maximum amount and by selec¬ 
tion, so far as the milk, mash, and grain mixtures were concerned. The 
rape, finely chopped, and the milk were likewise kept in separate con¬ 
tainers. Thus, where the chicks in their first eight weeks are given all 
the sour skim milk and green feed they will consume, there will be required 
approximately 3 gm. of grain and mash per gram of gain in body weight. 
In these two lots it was found that 75.2 per cent of the carbohydrates 
were digested and 80.2 per cent of the fat. These are the averages for 
the eight periods, the digestibility varying from period to period. 
The methods used to separate the ammonia and uric acid of the feces 
from the undigested protein of the feed were not considered to be suffi¬ 
ciently accurate to give here. The problem of separating the mineral 
elements from those passed out with the feces unused is a quite different 
matter. If it were possible to separate the urine from the feces by 
surgical interference, there would yet remain that eliminated by way 
of the bowel, which could not be separated from that taken with the food 
and not utilized. At this time there seems to be only one practical way 
to measure mineral requirements—that is, by comparing the intake with 
the outgo and the amount required to construct the tissue gain, and to 
study the mineral balances left over unaccounted for. 
