692 PHYSIOLOGY 



apparatus can be built of any size. In the apparatus of Tigerstedt 

 built on this plan the chamber had a capacity of 100-6 cubic metres, 

 and was, in fact, a small room. A similar respiratory apparatus has 

 been built by Atwater. 



IV. ZUNTZ AND GEPPERT'S METHODS. For many purposes 

 the methods devised by Zuntz and Geppert present many advan- 

 tages, especially when it is desired to take the respiratory ex- 

 changes in man or any animal during a limited period of time. The 

 subject of the experiment has his nostrils clamped and breathes 

 into and out of a face-piece. This face-piece is provided with 

 valves either of aluminium or of animal membrane, which serve 

 to separate the in-going from the out-going current of air. In 

 the course of the out-going current is placed a very delicate gas 

 meter which presents practically no resistance to the air current. 

 A branch from the efflux tube passes to a gas analysis apparatus. 

 By an ingenious method it is arranged that an aliquot part of the 

 whole of the out-going air is drawn off into this apparatus, so that 

 the experiment can be interrupted at any time, and the analysis 

 of this sample will give the average composition of the expired air, 

 and therefore, on multiplication by the total gas passing through 

 the gas meter, the total output of carbon dioxide during the course 

 of the observation. One advantage of this method is that the 

 apparatus is portable, and can be applied to the investigation of the 

 respiratory exchanges of patients in hospitals or of man or animals 

 while they are walking about. It has been used, for instance, by 

 Zuntz and his pupils in an interesting series of researches on the 

 gaseous metabolism of men at high altitudes. 



By means of one or more of these methods we may arrive at a 

 correct idea of the total income and output of an individual for periods 

 of many days. The following details by Tigerstedt may serve as an 

 example of the results obtained in such an experiment. The experi- 

 ment lasted two days. The subject was a man of twenty-six years 

 of age, weighing about 65 kilos, who had previously taken no food 

 for five days. The Tables on p. 693 represent his material income and 

 output. 



As we should expect in a man who had fasted five days, this balance- 

 sheet shows a marked retention of the food taken in, i.e. a marked 

 excess of income over output. Thus of the nitrogen ingested, 13 grm., 

 which is equivalent to 81 -3 grm. of protein, was retained ; of the 

 carbon, 302 grm. was retained. Of this 302 grm., 42'7 grm. would 

 be contained in the 81'3 grm. of protein, so that the rest of the carbon, 

 namely, 259- 6 grm., was probably laid down in the form of fat. 

 This would correspond to 339 grm. of fat. Of the salts contained 

 in the ash of the food, 25 grm. were retained in the body. The 



