APPARATUS AND METHODS USED IN THIS RESEARCH. 59 



The apparatus was so sensitive that even the slight movements due 

 to respiration are clearly indicated, especially in the quiet period 

 between 4 h 12 m p. m. and 4 h 45 m p. m. It will be seen by this curve 

 that there were several major changes in the position of the infant's 

 body which resulted in a total displacement of the level of the curve. 

 Shortly afterward, air was released through the tee tube and the pointer 

 was brought back to the original level. In any attempt to quantify 

 the values of the different periods, these displacements of the curve 

 due to major movements should be taken into consideration. A move- 

 ment may not be sufficiently great to produce a considerable amplitude 

 of the pointer and yet be produced by a shifting of the whole body, thus 

 establishing a new, permanent center of gravity of the system. Obvi- 

 ously, in this case, a greater displacement could reasonably be supposed 

 to have taken place than when the line returned to the same level. 



It should be stated that the ocular method of observation of infants 

 or animals during respiration experiments is most illusive and unsatis- 

 factory. We have repeatedly seen experimental periods when a careful 

 observer, even though watching the infant continuously, was unable 

 to record a perceptible movement other than those of respiration, and 

 yet the suspended crib, pneumograph, and tambour have recorded 

 distinct and persistent muscular tremors, accompanied in all cases by 

 an increasing pulse-rate and increased metabolism as measured by the 

 oxygen consumption and the carbon-dioxide production. While, there- 

 fore, careful ocular observations, such as were made in the earlier 

 experimenting at Wesleyan University in Middletown, Connecticut, 

 are of great value in interpreting the gross metabolism, for extremely 

 accurate observations the graphic method alone insures scientifically 

 exact results. It is furthermore obvious that the sensitivity of the 

 graphic method makes the continuous attention of an observer unnec- 

 essary, as the record of body movement is directly written without 

 bringing the personal equation in any way into play. 



WARD CRIB RECORDER. 



The relationship observed between the graphic tracings of the muscu- 

 lar activity and the katabolism indicated the possible value of recording 

 the activity of the infant throughout the day when it was not inside 

 the respiration chamber. Accordingly, to assist in settling some com- 

 plicated problems of nutrition, a special apparatus was devised and 

 set up in the children's ward of the hospital in order to obtain a con- 

 tinuous graphic record of the muscular activity of the infant. 



This apparatus, which was designated the "ward crib recorder," 

 consisted of a small crib, one end of which rested on two hardened steel 

 points and the other was suspended by a strong spiral spring. The 

 movements of the crib due to the activity of the infant were graphically 



