46 GASEOUS METABOLISM OF INFANTS. 



dioxide absorbing system owing to the excess water absorbed. If the 

 routine with the Williams and the soda-lime bottles is carried out as 

 previously outlined, no difficulty is experienced, but it is advantageous 

 occasionally to test the efficiency of the apparatus for absorbing carbon 

 dioxide and water-vapor. Consequently, in testing for leaks it is 

 advisable to weigh the sulphuric-acid and soda-lime vessels separately, 

 and continue passing the air through the system for a half hour. Under 

 these conditions, the loss in weight of the soda-lime vessel should of 

 course be exactly counterbalanced by the increase in weight of the 

 accompanying Williams bottle. With all of the experiments with 

 infants here reported, this procedure was followed out every morning. 

 It is needless to say that such precautions are no longer necessary, but 

 inasmuch as this was the first year that the apparatus was used in the 

 present form we considered it advisable to obtain this control before 

 each experiment. 



ALCOHOL CHECK TESTS. 



The large respiration calorimeters in this laboratory have all been 

 controlled by alcohol check tests as to their capability for measuring 

 the carbon dioxide and the water-vapor produced, oxygen absorbed, 

 and heat eliminated by the subject inside the chamber; we therefore 

 hoped to secure as satisfactory control tests for this small respiration 

 apparatus when used for infants. One of the greatest difficulties which 

 immediately presented itself was that of developing inside the respira- 

 tion chamber a known amount of carbon dioxide and absorbing a 

 known amount of oxygen. A simple method for this would have been 

 to place inside the respiration chamber an alcohol lamp and let it burn 

 for several hours, noting the loss in weight of the lamp. It should be 

 observed, however, that this respiration chamber is used for the most 

 part during experiments with half-hour periods. We considered it 

 unfair, therefore, to make an alcohol check experiment covering several 

 hours and assume that the results showed that the apparatus would be 

 equally as satisfactory for half-hour periods. The same problem arose 

 in connection with the development of our first respiration apparatus 

 for man, 1 and the difficulty was then overcome by burning a known 

 amount of ether vapor. By reference to this earlier test, it will be seen 

 that the special form of combustion chamber then used was perfectly 

 comparable with the respiration chamber employed for infants. But 

 the difficulties incidental to cooling the intense ether flame and making 

 all the connections satisfactory rendered it practically impossible for 

 us to carry out these tests in the hospital. 



For many years an attempt has been made to secure some method 

 for obtaining the actual amount of alcohol burned in a small lamp inside 

 the respiration chamber in periods as short as 30 minutes. In lieu of 



JBenedict, Am. Journ. Physiol., 1909, 24, p. 372. 



