• The maintenance df a IJealthy, body may be stated as an equation' bf force, and, by the doctrine of the i correction of forces, an equation of heat. We-ift compelled in dealing with the ihdei_ria|le property of life— i.e., vitality— to. sbi»}\fij f on the idea and grapple with its formula, as oiir want of knowledge o£ the" truth w\jl beet enable us. Itjs not the. whole tru^h. to qay, that the equation.of, internal and External heat is the problem qt health prgterya tipn, be cause heat is only,onefonn bftnotion,and, as regards>the phenomena: of Ufe,.electri city, magnetism, psychic, and nWe forces, whatever these .1 may be, ,are factors in the production of the result; but hfcat.is the readiest expression,' and, so fa. as\we know, plays the most prpmiuentparf i.h.Jhe main tenance of the health. Therefbr^it is not only permissible, bht.Bcie'ntifically accurate, to lay great stress on this factor— iaraely, temperature— in dealing; with the problem of avoiding cold and preserving a \olmal state of vitality. There are, accordingly, three propositions which it- seems Well -to press on public attention at a season Vhon great and sudden changes of external fcehipefature lieset us, and the perils conse quent on such changes are especially nf c. The chief, ana! in one sense the only source !of animal heat, ' is within ' lis. We w«ar clothes to prevent the radiation of. he^t generated within our bodies to the objects around, tha state of nature, even in the tropics, it suffices, to-dispense with clothing in order to be nor^ialjy^ temperate; but the ! usa of sdnshades^and puggaries niay#ei-ve ' as an illusti ation of' the: 'Use' of clotbfbj| or apparatus to, prevent the access of heat from without. Practically the human organism.must be maintained at a tempera ture equal tp 96'5deg. p_ Fahrenheit in all climates. The dffe_«rices of the normal temperature are irvry emaj). What is then required is as follows r ! The I !). dy' ] nilißt generate enough heat, by the conversion of food into 'heat, or work intq heat, to -raise the body, to the normal standard; ''pjus whatever may. be lost to surrounding objects. The use , of ..', non-conducting clothes may minimise :. the loss, perhaps prevent it altogether, :. but this will not secure- a healthy temperature unless the organism generates heat sufficiently for the supply which the conditions of life demand. 