i86 SECTIONAL ADDRESSES 



money on novel apparatus if it can possibly be avoided, though when 

 apparatus is provided, as experience shows, it will be freely used. It is 

 interesting that this slow application of discovery has been noted in com- 

 mercial spheres, and in a recent research benefaction to the Royal Society 

 part of the money can be used for popularising the results of research. 

 Such a provision is eminently desirable in medicine, and, in commending 

 it to the pious benefactor, I would point out thai much good could be done 

 by a comparatively small sum of money, since in the first place it need only 

 be applied to the voluntary teaching hospitals. When once the medical 

 student — the future doctor — has become accustomed to a new method or 

 a new apparatus, its spread throughout the country cannot be so long 

 delayed. 



Indirect Calorimetry. 



In estimating the heat production of an individual the oxygen intake 

 and the carbon dioxide output are measured. After allowing for protein 

 metabolism the oxygen intake is converted into calories of heat generated, 

 by multiplying it with a factor which depends on the respiratory quotient 

 (volume of COg produced/volume of Og absorbed). These multiplying 

 factors were calculated originally by Zuntz and Schumburg (1901) ^ and 

 are based upon (a) the heats of combustion of carbohydrate and fat, (b) the 

 chemical composition of carbohydrate and fat, and [c) the theory that 

 when the respiratory quotient has the value unity carbohydrate alone is 

 oxidised in the body and when the respiratory quotient has a value equal 

 to 0-707 fat only is being oxidised, and at intermediate values of the 

 respiratory quotient corresponding proportions of carbohydrate and fat 

 are being oxidised. This method of calculating the heat produced by 

 an individual is known as indirect calorimetry. The basal metabolism or 

 basal metabolic rate of American authors or ' standard ' metabolism of 

 Krogh and Lindhard is at present defined as heat production in the 

 morning before breakfast, fourteen to sixteen hours after the last meal of 

 the previous day (the post absorptive condition) with the subject; lying at 

 rest. 



The theory that the respiratory quotient, the term introduced by 

 Pfliiger, indicates the proportion of carbohydrate and fat that is being burnt 

 in the body has been evolved in physiology since Regnault and Reiset's 

 observations (1849) ^^'^ Reiset's observations (1863) on various animals. 

 These authors found that the proportion of carbon dioxide given out to 

 the oxygen taken in depended on the food taken rather than on the type 

 of animal investigated. In rabbit D, for example, this ratio — in other 

 words, the respiratory quotient was 0-95 when eating carrots, 0-997 with 

 bread and oats and o • 707 when hungry. In the case of a dog F, with 

 bread the respiratory quotient was 0-943, when hungry 0-724, and with 

 mutton fat 0-694. In 1898, M. S. Pembrey, in Schafer's Textbook of 

 Physiology, wrote that ' an animal fed on a vegetable diet has a quotient 



^ Few references are given in this Address as they appear in Guy's Hospital 

 Reports, 1934-37: 84, 473; 85,56, 447; 87, 151- 



