1061 



THORAX. 



Fig. 702. 



ft. in. ft.-in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. 'ft. in. ft. in. ft. in. ft. in. ft. in. 

 ..... too 5051 525354 5556 57 58 5 95 10 511 60 

 Heights. 5 o 5152 5354555657 58 59 5 10 5 11 606 + 



Inspiratory power of the healthy and diseased compared. 



OF THE RESPIRATORY VOLUMES. For 

 1500 years, from the time of Galen to Robert 

 Boyle, naturalists, physicians, and philoso- 

 phers disputed the simple operation of draw- 

 ing air into the thorax. There were three 

 explanations given : First, " That by the dila- 

 tations of the chest the contiguous air is thrust 

 away, and that, pressing upon the next air to 

 it, and so onwards, the propulsion is continued 

 till the air be driven into the lungs, and so 

 dilate them." 



Secondly, That the chest is like a pair of 

 common bellows, " which comes therefore 

 to be filled because it was dilated." 



Thirdly, That the lungs are like a bladder 

 " which is therefore dilated because it is filled." 



The great philosopher Boyle adopts the bel- 

 lows' action viz., that the lungs are filled with 

 air, because the chest is dilated, and that with- 

 out the motions of the thorax they could not 

 be filled. " Indeed," says Boyle, " the dia- 

 phragm forms the principal instrument of 

 ordinary and gentle respiration, although to 

 restrained respiration, if I may so call it, the 

 intercostal muscles, and perhaps some others, 

 may be allowed eminently to concur." * Co- 

 temporary with Boyle, we find Richard 

 Lower f (1667) correctly understanding the 

 respiratory action; he makes a dog breathe 

 like a broken-winded horse, by dividing the 

 phrenic nerve. What Boyle and Lower demon- 

 strated, every one nowbelieves withoutdispute; 

 yet it took 100 years' disputation, through a 

 number of unfounded hypothetical and contra- 

 dictory speculations, before the truths which 

 Boyle and Lower promulgated were received. 

 As late as the eighteenth century, little more 

 than one hundred years ago (A. D. 1737), 

 it was stated in the Gulstonian Lectures 

 before the Royal College of Physicians that 

 there was air between the pleura; J, a con- 

 dition which we now know is almost instant 



* Boyle's Life and Works, fol., Loud. 1744, vol. i. 

 p. 64. 



f Phil. Tr. Abr., vol. i. p. 179. 



j Hoadly, Lee. on Resp., 4to, 1740, Lond., p. 11, 

 et seq. 



death. The first great epoch in the history 

 of respiration was at the time of Harvey 

 (1628), when he published his first work on 

 the circulation of the blood, though at this 

 time he did not stand commended for his 

 discovery ; for most persons opposed it ; 

 others said it was old ; and the epithet " cir- 

 culatory' in its Latin invidious signification, 

 was applied to him. We know respiration 

 depends upon the weight of the air; and 

 at a very remote period air was known to 

 possess the quality of weight. Aristotle and 

 other ancient philosophers expressly speak 

 of the weight of the air. The process of re- 

 spiration is attributed by an ancient writer to 

 the pressure of the atmosphere forcing air 

 into the lungs.* Galileo was therefore fully 

 aware that the atmosphere possessed this pro- 

 perty ; yet when his attention was so immedi- 

 ately directed to one of the most striking effects 

 of it, he did not see its connection with respira- 

 tion. It was reserved for his pupil, Torricelli, 

 to discover (1643) the true law of atmo- 

 spheric pressure ; and as we can find no phi- 

 losophical reason assigned, prior to this date, 

 why air enters the lungs in inspiration, we may 

 date this as a first step in the advance of 

 knowledge upon our subject. Nevertheless, 

 no less an authority than Swammerdam 

 adopted, for upwards of twenty years after 

 this, the unphilosophical reasoning of Des- 

 cartes, that the air was forced into the lungs 

 by its increased density around the breast, oc- 

 casioned by the dilatations of the thorax, in 

 consequence of the elevation of the ribs. 



In 1667 some attention was paid to respira- 

 tion being maintained by distinct volumes of 

 air ; for Hook kept a dog alive with common 

 bellows by artificial respiration, f Fabricius, 

 in the beginning of the 17th century, cor- 

 rectly explained the action of the diaphragm. J 

 Borelli is the earliest physiologist (1679) who 



* Lardncr's Cyclop. Nat. Phil. Hydr. and Pneum. 

 p. 247. 



t Phil. Tr. Abr. vol. i. p. 194. 

 j De Resp. ii. c. viii. 



