APPARATUS AND METHODS USED IN THIS RESEARCH. 57 



A major change in position of the body of infants during the respira- 

 tion experiment is not ordinarily to be expected. With animals there 

 may be a change in the center of gravity of the body from one part 

 of the cage to the other, and consequently a distension or shortening 

 of the pneumograph with a corresponding increased or decreased ten- 

 sion on the tambour. Under these conditions it has been found advan- 



Fig. 5. Method of obtaining graphic record of muscular activity. 



L, crib; 0,'knife-edge support; M, spiral spring; N, pneumograph; P, tambour; T, tee for equal- 

 izing tension; H, cover of apparatus; K, water bath; G, ingoing air-pipe; G', outgoing air-pipe. 



tageous to place in the rubber tube leading from the respiration chamber 

 to the tambour a glass tee tube, with a short rubber tube and pinch- 

 cock on the open end. When the animal or infant has permanently 

 or temporarily settled down in a new position and the tambour shows 

 a distension or contraction, by opening the tee tube the normal pressure 

 can again be secured and the curves will proceed at the normal level. 



