RESPIRATION 



121 



FIG. 



use of this instrument pneumatic negative pressure actuates the lever 

 of a recording tambour. Another apparatus for recording the time- 

 relations, etc., of the respiratory rhythm is the stethograph, a variety 

 of which adapted to study the respiratory movements of the common 

 Southern lizard Anolis (" chameleon") is shown in Fig. 67. It con- 

 sists of levers resting against the sides of the thorax of the little animal, 

 which when separated lift a light lever writing as before on a smoked 

 drum rotating by clockwork. A third way of studying the respiratory 

 rhythm is to record by means of levers as before the movements up 

 and down of the reservoir which receives the air expired by the animal. 

 This is perhaps the least useful of the methods so far devised, for the 

 reason that the conditions are complicated by chemical as well as by 

 merely mechanical relations. The last of the methods invented, and 

 one which has told us much concerning the respiration of the smaller 

 mammals and of the movements 

 of the diaphragm especially, is 

 that of Head, who employed slips 

 of the rabbit's diaphragm to di- 

 rectly actuate levers recording as 

 before described. 



By these means, and by others 

 more or less similar, the chief 

 characteristics of the gross re- 

 spiratory movements have been 

 accurately studied. It has been 

 learned that in man the time of 

 inspiration is shorter than that 

 of expiration, the former being 

 to the latter about as 6 to 7. In 

 women, children, and old people 

 the difference is greater than this. 

 There is normally no pause be- 

 tween the cessation of inspiration 

 and the commencement of ex- 

 piration, for the parts put on stretch instantly recoil in their various 

 ways when the active contractile pressure stops at the end of inspiration. 

 Between the end of one expiration and the beginning of the next in- 

 spiration there is normally a short pause. In duration this may be 

 about one-fifth of the time required for a complete respiration. Ob- 

 servation of any normal stethogram, for example, that of Fig. 68, shows 

 well the respective characteristics of the inspiratory and of the expiratory 

 movements. The inspiratory phase is at first quick (as is shown by the 

 nearly vertical direction of the tracing), and then slightly slows to its 

 end ; it is also steady and interrupted less often than is the expiratory 

 phase. The expiratory movement is somewhat slower and more variable 

 in its different parts, as is shown by the tracing's obliquity and relative 

 irregularity. In looking over a number of stethograms traced from 



The Anolis stethogram. This shows one type 

 of 'the breath-movements of the common 

 Southern "chameleon." The right-hand line in 

 each curve is the inspiratory movement. To be 

 read from right to left. Original size. The 

 time-line is in seconds. (See other Anolis stetho- 

 grams in the Appendix.) 



