206 STUDIES ON RESPIRATION. XIIl 



The glass portion of the apparatus is rigidly fastened to the wooden 

 frame by two screws. The wooden frame, however, is not fastened 

 to the table but is allowed to move freely to compensate for the slight 

 motion produced by the compression of the rubber tube; without 

 this freedom of motion the connecting glass tubes might be broken. 



When a constant temperature must be maintained it may be 

 desirable to immerse the apparatus in water. The motor must then 

 be adjusted so that the arms which compress the rubber tubing 

 occupy a vertical position. The water should be contained in a 

 suitable glass vessel so arranged that the changes in the color of the 

 indicator may be readily observed. The buffer solutions must also 

 be immersed and should be placed beside the tube I which contains 

 the indicator. 



