METHODS AND APPARATUS. 29 



METHODS AND APPARATUS FOR STUDIES OF 

 MUSCULAR WORK. 



Judging from the results as published in the earlier literature and 

 summarized in the preceding section, there is apparently little choice 

 as to the various methods of study. A large majority of the observa- 

 tions have been made with the Zuntz respiration apparatus or some of 

 its modifications; it is obvious that any criticisms applying to this 

 apparatus affect greatly the averages of the values obtained with it. 

 While the construction of the Zuntz apparatus and the various types 

 of valves, particularly the later form of valve used by Durig, is such as 

 to eliminate resistance as far as possible, nevertheless the employment 

 of this type of apparatus for studying muscular work is distinctly open 

 to criticism. 



The use of a wet gas-meter of the size ordinarily employed with the 

 Zuntz respiration apparatus may be seriously objected to for muscular- 

 work experiments, since in these experiments the volumes of expired 

 air may exceed 80 or 90 liters per minute. The calibration of such a 

 meter at the rate of ventilation used in severe-work experiments is 

 by no means a simple matter, the ordinary method being to allow the 

 water in a 10-liter spirometer to flow out and draw the air in after it. 

 On the ordinary Elster gas-meter 10 liters correspond to one or at most 

 two revolutions of the drum, and the possibilities of error at the begin- 

 ning and the end in tests of this kind are obvious. Indeed, both Durig 

 and Zuntz have recognized this difficulty and, to avoid errors in the 

 measurement of the large volume of air expired from the lungs, have 

 made experiments with a very large gas-meter formerly used in studies 

 with horses. If the value obtained for the volume of air be too small 

 (and the error, if any, would be in this direction), obviously that for the 

 total metabolism will likewise be too small, and hence the values com- 

 puted for the horizontal kilogrammeter will be too low. 



The importance of knowing the energy requirement of the body for 

 direct forward progression is so great as to justify further observations 

 upon it, particularly if an apparatus is used in which an entirely dif- 

 ferent principle is employed for measuring the metabolism. One of 

 the main lines of research planned for the Nutrition Laboratory is a 

 study of muscular work in its various phases. Obviously innumerable 

 problems, of both physiological and economic importance, can be 

 studied with suitable apparatus. A special calorimeter has been 

 constructed in this laboratory for research on muscular work, but it is 

 not yet ready for actual use. Prior to experimentation with this 

 calorimeter, it seemed important to make a number of preliminary 

 studies of the metabolism during muscular work with the universal 

 respiration apparatus. This apparatus had previously been used in a 

 study of the metabolism incidental to riding a bicycle ergometer, in 



