APPARATUS AND EXPERIMENTAL TECHNIQUE. 29 



movements of the crib are transmitted through rubber tubing to a 

 tambour and small pointer outside the chamber. The adjustment is 

 so delicate that the slightest movement of the child changes the center 

 of gravity and a record is made by the pointer on the smoked paper 

 of a kymograph. Even the movements of the chest-wall due to res- 

 piration are frequently indicated on the kymograph record. A 

 straight line on the kj^mograph record thus shows that the child is 

 absolutely quiet. 



The pulse-rate is obtained with a stethoscope connected with the 

 observer outside the chamber by rubber tubing. Records were 

 made at intervals by the attendant nurse and show that muscular 

 activity instantly caused an increase in the pulse-rate. Accordingly, if 

 periods with a low pulse-rate and no activity are selected for compari- 

 son, we can be certain that the values represent the basal metabolism. 



This apparatus was employed at the Massachusetts General Hos- 

 pital for about two years and was also used for the observations at the 

 Directory for Wet-Nurses, the only change being that for the older 

 children a larger chamber was constructed. The apparatus as used 

 in actual w r ork at the Directory for Wet-Nurses is shown in figure 1, 

 with assistant in charge and nurse recording the pulse-rate. The end 

 of the chamber may be seen at the right, with the tambour and kymo- 

 graph for recording the muscular activity, and connections with the 

 nurse who is counting the pulse-rate. The ventilating system is at 

 the left, with the carbon-dioxide absorbers and spirometer on the 

 upper shelf of the table, and the water-absorbers and blower on the 

 lower shelf. The gas-meter for measuring the oxygen may be seen 

 in the center. 



For the experiments at the New England Home for Little Wanderers 

 a somewhat different form of chamber was used, i. e., a small clinical 

 respiration chamber, described in detail by Benedict and Tompkins, 1 

 and illustrated in figure 2. This is substantially a duplicate of the 

 apparatus used for studying the normal infants, with the exception 

 that the chamber is much larger and hence of a somewhat different 

 type of construction. In that used for the infants the cover shuts 

 down like the lid of a trunk, while in the apparatus employed for the 

 older children the cover is of a semi-cylindrical form and is suspended 

 by two ropes connected with a counterpoise, thus providing for raising 

 and lowering the cover. When the cover is lowered, it enters a 

 narrow water-seal which makes it air-tight. A rectangular window 

 in the cover provides for illumination. Figure 2 gives a general view 

 of the respiration laboratory at the New England Home for Little 

 Wanderers, with the respiration chamber at the right, and the venti- 

 lating and absorbing system at the left ; the kymograph and tambour 

 appear on a small table in the background. 



i Benedict and Tompkins, Boston Med. and Surg. Journ., 1916, 174, pp. 857, 898, and 939. 



