PART III. 



CRITICAL DISCUSSION OF RESPIRATION APPARATUS AND THEIR 



TECHNIQUE. 



In this investigation essentially two types of respiration apparatus 

 have been employed. One is constructed on the Regnault-Reiset prin- 

 ciple, sometimes designated as the "closed-circuit" or " direct" method; 

 the other is on the "open-circuit" plan or the so-called "indirect" 

 method, requiring the use of valves and apparatus to measure and 

 analyze the expired air. The first type is represented by the two forms 

 of the Benedict universal respiration apparatus (the tension-equalizer 

 unit and the spirometer unit) and by Holly's recent modification of the 

 tension-equalizer unit. The indirect type is represented by the Zuntz- 

 Geppert, Tissot, and Douglas methods. As the experiments carried out 

 in this investigation have shown that practically the same results can 

 be obtained with all of these methods, it is of interest to consider 

 the advantages and disadvantages of the different forms of respiration 

 apparatus regularly employed in various laboratories and clinics. In 

 this discussion, however, only those apparatus will be included which 

 have been used in this research. 



BENEDICT UNIVERSAL RESPIRATION APPARATUS. 



The spirometer form of the Benedict universal respiration apparatus, 

 which is coming more and more into use, has certain special advantages. 

 One of these is the facility with which respiration experiments with 

 periods of short duration may be made and the results calculated. 

 The ease and rapidity with which this apparatus may be manipulated 

 are especially appreciated by those who are required to make long 

 experiments in which the later periods depend upon the results of those 

 preceding. In many of the experiments in this laboratory, as, for 

 instance, when the effect of a superimposed factor is being studied, 

 it is necessary to know as soon as possible the results of the first two or 

 three periods, so as to assure the experimenter that an accurate base- 

 line has been established before the experiment is continued under the 

 changed conditions. With this apparatus it is possible, with the help 

 of one laboratory assistant, to make a series of three 15-minute periods 

 and to calculate the results in the minimum time of an hour and a 

 half. In fact, the results of the first two periods may be calculated 

 while the succeeding periods are being carried out. In a long series of 

 experiments made with a fasting man it was possible in every case to 

 complete the calculations of the first two 15-minute periods by the end 

 of the third period. This is possible with no other apparatus now in 

 use for the determination of the respiratory exchange. 



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