36 GASEOUS METABOLISM OF INFANTS. 



to a 2-way valve, V h where it may be deflected through either of the 

 soda-lime bottles Di or D 2 , in which the carbon dioxide is absorbed. 

 Since the reagent must be somewhat moist to facilitate the absorption, 

 it gives up water-vapor to the dry air-current, which must in turn be 

 absorbed by sulphuric acid in the Williams bottles E x or E 2 . The air 

 next passes through the 2-way valve, V 2 , and enters a small can, F, which 

 contains dry sodium bicarbonate, the unweighable but noticeable sul- 

 phuric-acid odors being effectually removed by this means. The air 

 then returns to the chamber through the by-pass J; or, if it is desired 

 to moisten the air, the current can be deflected by closing the valve R 

 in the by-pass J, so as to pass all of the air through distilled water in the 

 Williams bottle, K. The air is now free from carbon dioxide and con- 

 tains the water-vapor added in passing through K, but is still deficient 

 in oxygen. This deficiency is made up by admitting oxygen from a 

 cylinder, L, of compressed gas. The air thus enters the respiration 

 chamber at 7, somewhat moist and with approximately the normal 

 percentage of oxygen. 



Either series of absorbers may be used as desired, for if the air-current 

 has been passing through the series A and E x for a given experimental 

 period, the air can be instantly deflected through the series D 2 and E 2 , 

 by turning simultaneously valves Vi and V 2 - As actually constructed, 

 Vi and Vi are connected by a long rod, so that they may be thrown 

 simultaneously by one movement of the hand. 



Since the air-current is entirely closed, a small spirometer, S, is 

 attached at the upper right-hand corner of the respiration chamber, 

 thus providing for any expansion or contraction of the air. A ther- 

 mometer, T h in the cover of the chamber, and a second thermometer, 

 T 2 , in the outgoing air, serve to indicate the temperature changes, 

 while the manometer, M, shown below the spirometer, indicates the 

 pressure of the air in the chamber. 



By noting the increase in weight of the absorbers, D x and Ei or D 2 

 and E 2) the amount of carbon dioxide absorbed is known. It is possible 

 that the amount of water-vapor given up by D x to the dry air passing 

 through it may be actually more than the amount of carbon dioxide 

 absorbed, so that the bottle D Y may lose in weight; on the contrary, 

 the water-vapor given up is immediately absorbed by E h and hence the 

 algebraic sum of the weight of the two bottles gives the weight of the 

 carbon dioxide absorbed. Usually both bottles are weighed on a 

 balance at the same time. The loss in weight of the cylinder L indi- 

 cates the amount of oxygen absorbed, corrections being made for any 

 variations in temperature and barometric pressure, or in the composi- 

 tion of the air inside the respiration chamber. 



In figure 2 a general idea is given of the method of suspending the 

 crib upon a stout spiral spring, U, at one end and a knife-edge, G, at 

 the other. Alongside of the spring U is a pneumograph, H, the disten- 



