226 



CHEMISTRY OF RESPIRATION. 



bands that are stretched for high notes, and are alternately approximated and 

 separated, while characteristic, inarticulate sounds are emitted from the larynx, 

 with vibrations of the soft palate. The mouth is usually open, and the face is 

 drawn into a characteristic position by the zygomaticus major (not the risorius 

 muscle). Laughing is usually aroused involuntarily by agreeable conceptions, or 

 by feeble, sensory irritation, such as tickling. It may to a certain extent be 

 repressed by the will, as by forcibly closing the mouth and holding the breath; 

 also by painful irritation of sensory nerves, as by biting the tongue or the lips. 



Yawning consists in a prolonged, deep inspiration, with the mouth, the 

 palatal arch and the glottis widely open, successively calling into play numerous 

 inspiratory muscles. Expiration is shorter, and both are often accompanied by a 

 prolonged, characteristic sound. There also occurs frequently a general stretching 

 of the bodily muscles. The act is always involuntary, being usually incited by 

 sleepiness or monotony. 



CHEMISTRY OF RESPIRATION. 



The problem here is to estimate qualitatively and quantitatively 

 the gases expelled during respiration. If the results be compared with 

 the gaseous composition of inspired, atmospheric air, a picture may be 

 obtained of the interchange of gases occurring during respiration. 



QUANTITATIVE ESTIMATION OF THE CARBON DIOXID, THE 



OXYGEN, AND THE AQUEOUS VAPOR IN GASEOUS 



MIXTURES. 



Estimation of the Carbon Dioxid. 



The volume of carbon dioxid may be estimated by means of Vierordt's 

 antkracometer (Fig. 85, II). The gaseous mixture is received and enclosed in a 

 graduated tube r r, previously filled with water, and provided at one end with 



T[ 



FIG. 85. I. Apparatus for the Collection of Expired Air (after Andral and Gavarret). 

 II. Carl Vierordt's Anthracometer. 



a bulb of known capacity. The bottle n, filled with a solution of potassium 

 hydrate, is then screwed on the end-piece h. The stop-cock is opened, and the 

 potassium-solution is allowed to run up into the tube, the latter being agitated 



