22 FAMILIAR LETTERS ON CHEMISTRY. 



its action, while, in hot climates, the necessity of labor to provide food is far less 

 urgent. 



Our clothing is merely an equivalent for a certain amount of food. The more 

 warmly we are clothed the less urgent becomes the appetite for food, because the 

 loss of heat by cooling, and consequently the amount of heat to be supplied by the 

 food, is diminished. 



If we were to go naked, like certain savage tribes, or if in hunting or fishing we 

 were exposed to the same degree of cold as the Samoyedes, we should be able with 

 ease to consume ten pounds of flesh, and perhaps a dozen of tallow candles into 

 the bargain, daily, as warmly clad travellers have related with astonishment of 

 these people. We should then also be able to take the same quantity of brandy or 

 train oil without bad effects, because the carbon and hydrogen of these substances 

 would only suffice to keep up the equilibrium between the external temperature and 

 that of our bodies. 



According to the preceding expositions, the quantity of food is regulated by the 

 number of respirations, by the temperature of the air, and by the amount of heat 

 given off to the surrounding medium. 



No isolated fact, apparently opposed to this statement, can affect the truth of this 

 natural law. Without temporary or permanent injury to health, the Neapolitan 

 cannot take more carbon and hydrogen in the shape of food than he expires as 

 carbonic acid and water ; and the Esquimaux cannot expire more carbon and 

 hydrogen than he takes into the system as food, unless in a state of disease or of 

 starvation. Let us examine these states a little more closely. 



The Englishman in Jamaica perceives with regret the disappearance of hia 

 appetite, previously a source of frequently recurring enjoyment ; and he succeeds 

 by the use of cayenne pepper and the most powerful stimulants, in enabling 

 himself to take as much food as he was accustomed to eat at home. But the whole 

 of the carbon thus introduced into the system is not consumed ; the temperature 

 of the air is too high, and the oppressive heat does not allow him to increase the 

 number of respirations by active exercise, and thus to proportion the waste to the 

 amount of food taken ; disease of some kind, therefore, ensues. 



On the other hand, England sends her sick to southern regions, where the amount 

 of the oxygen inspired is diminished in a very large proportion. Those whose 

 diseased digestive organs have in a greater or less degree lost the power of bringing 

 the food into the state best adapted for oxidation, and therefore are less able to 

 resist the oxidising influence of the atmosphere of their native climate, obtain a 

 great improvement in health. The diseased organs of digestion have power to 

 place the diminished amount of food in equilibrium with the inspired oxygen, in 

 the mild climate ; while in a colder region the organs of respiration themselves 

 would have been consumed in furnishing the necessary resistance to the action of 

 the atmospheric oxygen. 



In our climate, hepatic diseases, or those arising from excess of carbon, prevail 

 in summer ; in winter, pulmonary diseases, or those arising from excess of oxygen, 

 are more frequent. 



The cooling of the body, by whatever cause it may be produced, increases the 

 amount of food necessary. The mere exposure to the open air, in a carriage or on 

 the deck of a ship, by increasing radiation and vaporisation, increases the loss of 

 heat, and compels us to eat more than usual. The same is true of those who are 

 accustomed to drink large quantities of cold water, which is given off at the tem- 

 perature of the body, 98.5 degrees. It increases the appetite, and persons of weak 

 constitution find it necessary, by continued exercise, to supply to the system the 

 oxygen required to restore the heat abstracted by the cold water. Loud and long 

 continued speaking, the crying of infants, moist air, all exert a decided and 

 appreciable influence on the amount of food which is taken. 



We have assumed that it is especially carbon and hydrogen which, by combining 

 with oxygen, serve to produce animal heat. In fact, observation proves that the 

 hydrogen of the food plays a not less important part than the carbon. 



The whole process of respiration appears most clearly developed, when we 

 consider the state of a man, or other animal, totally deprived of food. 



The first effect of starvation is the disappearance of fat, and this fat cannot b6 

 traced either in the urine or in the scanty faeces. Its carbon and hydrogen have 

 been given off through the skin and lungs in the form of oxidized products ; it is 

 obvious that they have served to support respiration. 



In the case of a starving man, 32 ounces of oxygen enter the system daily, and 

 are given out again in combination with a part of his body. Currie mentions the 

 ease of an individual who was unable to swallow, and whose body lost one hundred 

 pounds in weight during a month ; and, according to Martell (Trans. Linn. Soc., 



