tion, it passes into another form
of force--mechanical, or motive power. The heat generated within the
body is absorbed by the liquid water, the conversion of the latter into
vapor follows, and both the heat and the water, in their altered forms,
escape through the pores.

_Fatty food necessary in cold climates._--As a grave objection against
the chemical theory of heat, it has been urged that rice--the pabulum of
hundreds of millions of the inhabitants of tropical regions--contains an
exceedingly high proportion of heat-giving substances. I have, however,
great doubt as to rice ever forming the exclusive food of those people,
without their health being impaired in consequence of the deficiency in
that substance of the plastic elements of nutrition. Indeed I believe
it is a great mistake to assert that the natives of India live almost
exclusively on rice. This article, no doubt, forms a large proportion of
their food, but it is supplemented with pulse (the produce of leguminous
plants), which is rich in flesh-forming materials, also with dried fish,
butter, and various kinds of vegetable and animal food rich in nitrogen.
The innutritious nature of rice is clearly shown by its chemical
composition, and so large a quantity of it must the Hindu consume in
order to repair the waste of his body, that his stomach sometimes
acquires prodigious dimensions; hence the term "pot-bellied," so often
applied to the Indian ryot. I doubt very much, however, if the stomach
of the Hindu, large as it is, could accommodate a quantity of rice, the
combustion of which would produce a very excessive development of heat.
This substance, when cooked, contains a high proportion of water, the
evaporation of which carries off a large amount of the heat generated
by the combustion of its respiratory constituents. The amount of motive
power developed by the Hindu is small as compared with that which the
European is capable of exerting; hence he has less necessity for a
highly nitrogenous diet. On the whole, then, I am disposed to think
that the food of the natives of tropical climates contains sufficient
nitrogenous matters to effectually build up and keep in repair their
bodies; it also appears clear to me that the amount of heat developed
in their bodies is not excessive, and that it is readily disposed of
in converting the water, which enters so largely into their diet, into
vapor. The proportion of plastic to non-plastic elements in the diet
of