RESPIRATION. 



per minute, until the subject begins to make respiratory efforts of 

 his own or no doubt remains that life is extinct. 



XI. ESTIMATION OF CO 2 AND H 2 O EXPIRED IN A GIVEN TIME. 



The estimation of carbon dioxid and water expired by a small 

 animal in a given time may be conveniently done by each group 

 of students. Absorption tubes, made for the purpose, may be 



FIG. 38. Apparatus for Estimating the Water and Carbon Dioxid Eliminated from 

 the Lungs of a Small Animal. Described in text. 



bought at a moderate price, as well as the respiratory chamber 

 with air inlet and outlet and tightly fitting stopper. A schematic 

 sketch of the apparatus used is given in Fig. 38. 



The chamber C is intended for holding some small animal, such 

 as a rat or a mouse. This is tightly stoppered, the stopper being 

 perforated for the passage of two tubes (a) the air-intake tube, 

 which passes nearly to the bottom of the chamber, and (b) the air- 

 outlet tube, which begins near the upper part of the chamber. The 

 air-intake tube is connected with two absorption tubes i , contain- 

 ing pumice stone soaked in sulphuric acid, for absorbing the moist- 

 ure from the air which passes to the respiratory chamber, and 2, 

 containing soda lime for absorbing the carbon dioxid of the in- 

 spired air. 



The air outlet tube is also connected with two absorption tubes 

 3, containing sulphuric acid for absorbing the water of the expired 

 air, and 4, containing a strong solution of sodium hydrate for ab- 



