and of their Increase ichilst Fattcniufj. 
479 
paring; this with tlio estimated amount ol" fat in the increase, it 
appears (see Table XVIII.), that there were, on the average, 4 
to 5 times as much fat stored up as there was so supplied in 
the food. In the case of the analysed fat pig, the result was 
obtained in as direct a manner as the nature of the question 
admits of; and it appeared that 405 parts of fat were stored up, 
for 100 consumed in food. The average of the other experi- 
ments shows 472 parts of fat in increase for 100 ready-formed in 
food. 
It seems not improbable that fat may be jwodiiccd in the 
animal body by the aid of the products of transformation within 
it of nitrotjcnous compounds. But it is probable, that at least 
the main source of the produced fat is the ?;o/«-nitrogcnous con- 
stituents of the food. Of these, particularly in the fattening 
food of the pig, the most prominent item is starch. We adopt 
this substance, therefore, as the basis of the illustrations of the 
probable amount of the constituents of the food involved in 
the formation of the pivdnccd fat, in the experiments in ques- 
tion. 
For practical purposes it may be assumed, that 2i parts of 
starch will be required for the formation of 1 part of the mixed 
fats of the animal body, when these have their source in that 
substance. If fat be formed from nitrogenovs compounds, a Jess 
amount of the dry substance of the food will then be required 
for the formation of a given amount of lat, than when it is pro- 
duced from starch. If sugar be the source of the fat, a slightly 
larger quantity than of starch will be required. Of the pectine 
bodies, again, which enter so largely into the roots that fre- 
quently constitute a large proportion of the fattening food of 
oxen and sheep, the quantity required would be still more than 
of sugar. 
Table XXI. shows the estimated amount of fat stored up in 
increase for 100 dry matter of food, the amount of ready-formed 
fat in the food, the amount of fat that must have been produced 
from other compounds, and the amount of starch required if 
the produced fat were formed from it, in the cases of the nume- 
rous experiments with pig. 
It is estimated that, in the case of the single analysed fat pig, 
100 dry substance of the fattening food gave 13"2 parts of fat in 
increase. Of this, only 3"26 parts could have been derived 
from ready-formed fat in the food, even supposing the whole so 
supplied had been taken up. At least 9'94 parts must, there- 
fore, have been formed in the body of the animal from some 
other constituent or constituents. If the constituent in question 
were starch, it would require (at the rate of 2\ parts starch 
for 1 of fat) 24' 8 parts of that substance for the formation 
of 
