CRITICAL DISCUSSION OF RESPIRATION APPARATUS. 257 



the standpoint of an air-tight closure, but its use may be disagreeable 

 to the subject. The glass nosepiece is not so practicable as the pneu- 

 matic nosepiece, which, with proper precautions, can be made to con- 

 form closely to the inequalities in the surface of the nostril and is the 

 most comfortable for the average subject. 



GAS ANALYSIS. 



Practically all methods of determining the respiratory exchange 

 require the use of gas-analysis apparatus in one form or another. Even 

 determinations made with apparatus constructed on the Regnault- 

 Reiset principle may involve gas analysis, for Roily, in his adaptation 

 of the Benedict respiration apparatus, has considered it necessary to 

 make air analyses to find whether or not the apparatus is air-tight. 

 The difficulties experienced by many investigators with such appa- 

 ratus led to the development of the Benedict respiration apparatus, for 

 it is considered that the general construction and technique of this 

 apparatus make gas analysis unnecessary in its use. 



It is frequently claimed that gas analysis requires special technique, 

 which manjr people are unable to acquire. It must be admitted that 

 in going over the results of analyses obtained with various kinds of 

 gas-analysis apparatus, it is not so easy to find duplicate results as 

 would be expected. Another factor which must be taken into consider- 

 ation is not only the ease or the difficulty in obtaining results, but also 

 the amount of work involved. All analysts will agree that gas analy- 

 sis is one of the most tedious operations connected with the determina- 

 tion of the respiratory exchange and becomes very monotonous when 

 continued for any length of time. In fact, in this laboratory it has 

 been found advisable to vary the work of the analysts, so that they 

 may operate with the highest efficiency and with the least physical 

 strain. At the same time it is perfectly logical to conclude that if an 

 individual can not make gas analyses well enough to obtain accurate 

 results, he should not be engaged in the study of the respiratory ex- 

 change, for it is probable that his results will be similarly inaccurate, 

 as the technique of such investigations is somewhat difficult. 



In this research two types of gas-analysis apparatus were used and 

 the criticisms here set down will refer mainly to these two tj r pes. The 

 Zimtz gas-analysis apparatus' was employed in the first series of 

 comparison experiments with the Zuntz-Geppert method, 2 and very 

 fair results were obtained with it. When each division of the burettes 

 represents 0.02 c.c., it is quite possible to obtain duplicates to 0.02 

 per cent. The special advantage of this apparatus is the fact that the 

 analysis may be made in duplicate in one operation rather than by 

 drawing two samples and analyzing them successively. However, 

 this simply means that one operation has been carried out twice in 



'See description on p. 58. 2 See p. 119. 



