Introduction. 7 



large respiration chamber and, so far as the mechanics of respiration are con- 

 cerned, is substantially under no abnormal influence, the other in which the 

 products of respiration are conducted through a mouthpiece, nosepiece, or 

 mask, the latter has been used in by far the greater number of instances. 



Normal Activity Restricted by the Conditions of Experiments. 



Without attempting to go into a detailed discussion of the relative advantages 

 of the chamber method when compared with the methods involving the use 

 of special breathing appliances, it may be said that the abnormal respiration 

 resulting from the insertion of special appliances into the nostrils, and par- 

 ticularly into the mouth, may in part be compensated by the fact that the 

 experiments are of short duration, and hence the subjects can live normally 

 between experiments, and move about as much as desired. When the subject 

 is confined inside the respiration chamber, on the other hand, it is necessary 

 to remain there for many hours, usually with enforced quiet and diminished 

 muscular activity. In neither case can the metabolism, strictly speaking, be 

 considered as determined under normal conditions. The daily activity of the 

 average man includes almost invariably some outdoor exercise, even if no 

 more than walking to and from his place of business. It also involves more 

 or less activity about the house or dwelling-place, in walking from one room 

 to another, dressing and undressing, partaking of the different meals, and the 

 innumerable little items of daily life. In the respiration chamber these are 

 in large part omitted. Consequently, in all of these studies it is obvious that 

 the metabolism is considerably less than that which would be found were the 

 studies made under absolutely normal conditions. In both methods of experi- 

 menting, muscular activity is at the minimum. 



It has been found, moreover, that even with experiments in which the gross 

 muscular activity appeared to be more or less constant from day to day, the 

 minor muscular movements, such as moving about in the chamber, crossing 

 the arms or legs, reading a book and turning its pages, result in a considerable 

 variation in the metabolism of so-called resting men. Hence it is clear that 

 in these experiments, in which the muscular activity is confined to the minor 

 muscular movements, the metabolism must be considerable less than that of 

 a man about his ordinary daily occupation, even if his work does not call for 

 sustained muscular effort. 



Nearly all of the appliances for studying the respiratory exchange, either 

 the chamber or the nose and mouth breathing type, do not permit of any major 

 muscular movements, but there is one noticeable exception to this, i. e., the 

 large respiration chamber of Sonden and Tigerstedt in Stockholm, an appa- 

 ratus that has recently been duplicated by Tigerstedt 1 in Helsingfors. The 

 chamber is of sufficient size to permit a person, or a number of persons, to 

 move about with considerable freedom. So far as the published reports of 



1 Tigerstedt, Skand. Archiv f. Physiol., 1906, 18, p. 298. 

 2 



