UNIVERSAL RESPIRATION APPARATUS. 21 



BENEDICT UNIVERSAL RESPIRATION APPARATUS. 



Two types of the Benedict universal respiration apparatus have been 

 used in this investigation : one, the tension-equalizer type and the other 

 the spirometer type. The tension-equalizer apparatus was the first one 

 to be developed and its use extended from about 1908 to 1912 ; the spiro- 

 meter type was developed hi 1911-12 and has been in use since that 

 tune. Both forms may be designated by the German word " Universal- 

 respirationsapparat." It has been the common practice in this labor- 

 atory to call them units and this term will be used in this publication, 

 i. e., tension-equalizer unit and spirometer unit, respectively. 



TENSION-EQUALIZER UNIT. 1 



This apparatus is essentially the same as the respiration portion of 

 the respiration calorimeters of this laboratory, except that it is con- 

 structed on a smaller scale and modified so that a subject can breathe 

 by means of a suitable connection into and out of a moving current 

 of air. The respiration may take place through the nose or mouth 

 or through both. The water-vapor is removed from the air-current 

 by sulphuric acid and the carbon dioxide is retained by soda-lime in 

 weighable containers. The oxygen content of the apparatus is main- 

 tained at a constant volume by admission of oxygen into the moving 

 current from a weighed cylinder or through a meter. The volume of the 

 air in the apparatus and also in the respiratory tract of the subject must 

 be the same at the end of the experimental period as at the beginning. 



GENERAL PLAN OF APPARATUS. 



The general principle of the apparatus and the course of the air- 

 current are shown diagrammatically in figure 2. The air expired by 

 the subject passes into the moving current of air and is carried into 

 the tension equalizer, then through the rotary blower, which keeps the 

 air of the apparatus in circulation. After leaving the rotary blower 

 it passes into the water absorber, where all the water in the air-current 

 is retained, and then goes through the carbon-dioxide absorber. In 

 the absorption of carbon dioxide, water- vapor is set free from the moist 

 absorbent and this water is removed in a second water-absorber. To 

 make the air respirable water-vapor is added to the air-current by 

 passing it through a water-container. The circulating air then passes 

 to the opening connected with the respiratory tract of the subject. 

 Oxygen is admitted into the air-current at a point near the tension 

 equalizer. 



The general construction of the apparatus and arrangement of the 

 several parts are shown in figure 3. The whole apparatus is mounted 

 on a movable table. On a shelf at the bottom are the rotary blower 



*A complete description of this apparatus has been given elsewhere. See Benedict, Am. Journ. 

 Physiol., 1909, 24, p. 345. 



