TRANSACTIONS OF SECTION A. 543 



7. R<"porl on Meteorological Observations on Ben Nevis. 

 See Reports, p. 93. 



8. Eeport on the Comparison and Redicction of Magnetic Observations. 



See Reports, p. 58. 



TUESDA Y. SEPTEMBER 16. 



Department I. — Physics. 

 The following Papers were read :— 



1. Animal Thermostat. By Lord Kelvin. 



A thermostat is an apparatus, or instrument, for automatically maintaining a 

 constant temperature in a space, or a piece of solid or fluid matter with varying 

 temperatures in the surrounding matter. 



Where and of what character is the thermostat by which the temperature of 

 the human body is kept at about 98'-4 Fahrenheit ? It has long been known that 

 the source of lieat drawn upon by this thermostat is the combination of food with 

 oxygen, when the surrounding temperature is below that of the body. The discovery 

 worked out by Lavoisier, Laplace, and Magnus still holds good, that the place of 

 the combination is chiefly in tissues surrounding minute tubes through which blood 

 circulates to all parts of the body, and not mainly in the place where the 

 furnace is stoked by the introduction of food, in the shape of chyle, into the 

 circulation, nor in the lungs where oxygen is absorbed into the blood. It is 

 possible, however, that the controlling mechanism by which the temperature is 

 kept to 98°-4 may be in the central parts, about, or'in, the pumping station (the 

 heart) ; but it may seem more probable that it is directly eflective in the tissues or 

 small blood-vessels in which the combination of oxygen with food takes place. 



But how does the thermostat act when the surrounding temperature is anything 

 above 98°'4 and the atmosphere saturated with moisture so that perspiration could 

 not evaporate from the surface ? If llie breath goes out at the temperature of the 

 body and contains carbonic acid, what becomes of the heat of combustion of the 

 carbon thus taken from the food? It seems as if a large surplus of heat must 

 somehow be carried out by the breath : because heat is beintr conducted in from 

 without across the skin all over the body ; and the food and drink we may suppose 

 to be at the surrounding temperature when taken into the body. 



Much is wanted in the way of experiment and observation to test the 

 temperature of healthy persons living in a thorouglily moist atmosphere at 

 temperatures considerably above 98°-4 ; and to find ho\v much, if at all, it is 

 above 98°-4. Experiments might also, safely I believe, be tried on healthy 

 persons by keeping them for considerable times in baths at 106° Fahr. with 

 surrounding atmosphere at the same temperature and thoroughly saturated with 

 vapour of water. The temperature of the mouth (as ordinarily taken in medical 

 practice) should be tested every two minutes or so. The temperature and quantity 

 and moisture and carbonic acid of the breath should also be measured as accurately 

 as possible. 



P.S., December h, 1902. — Since the communication of this note my attention 

 has been called to a most interesting paper by Dr. Adair Crawford in the ' Philo- 

 sophical Transactions' for 1871 (Hutton's Abridgments, vol. xv. p. 147), Experi- 

 ments on the Power that Ani7nals, 2rhen placed in certain circumstaiices, possess 

 of producing Cold. Dr. Crawford's title expresses perfectly the question to which 

 I desired to call the attention of the British Association ; and, ^s contributions 



