1056 



THORAX. 



rection of its fibres) the ribs. It may be said 

 to be both inspiratory and expiratory. 



IV. Infra- costales (Verheyen). In connec- 

 tion with the inner surface of the ribs (fig. 673.) 

 several small bundles of fleshy and tendinous 

 fibres, which are thus named, will be found ex- 

 tending over two, and in some instances over 

 three, intercostal spaces. They have the same 

 direction with the internal intercostals, and are 

 (properly) often described as parts of those 

 muscles. The fasciculi vary in size and number, 

 and may be found on any of the intercostal 

 spaces, except, perhaps, the first ; but they are 

 most constant on the lower ribs. 



Action. The same as the costal portion 

 of the internal intercostals, depressors of the 

 ribs and expiratory muscles. 



OF THE ELASTICITY OF THE RIBS. 



Elasticity depends upon reaction, and restores 

 in a contrary direction the force which have 

 been impressed ; the effect produced is com- 

 mensurate with the amount of the cause, and 

 the reaction can never take place so long as the 

 cause continues to be applied ; but immedi- 

 ately that cause ceases, the elasticity comes 

 into action. 



Inspiration is performed by the true inspi- 

 ratory muscles, and expiration, by the expira- 

 tory muscles, and the elasticity of the ribs 

 and their cartilages, together with the elasticity 

 of the lungs. We find a broad difference 

 manifested between the inspiratory and ex- 

 piratory power (TABLE R.), the latter exceed- 

 ing former by about one third. This differ- 

 ence is due to the elasticity of the ribs and 

 lungs associating their power with the ex- 

 piratory muscles. The combined elastic power 

 is very great ; we have examined it in two fa- 

 vourable cases, an hour after death, when 

 the bodies had not fallen one degree in 

 temperature. 



X. H., a young man, slightly built, erect 

 and well formed, set. 22, weight 9ist., height 

 5ft. lOin., vital capacity 235 cubic inches. 

 The absolute capacity of his chest was 248 

 cubic inches ; internal area 256in.; circumfe- 

 rence of the chest, over the nipples, in the or- 

 dinary state, alive 33 inches, dead 30^ inches. 

 After death we forced air into his lungs, whilst 

 the temperature of the body was still at 97. 

 The force resisting the introduction of this air 

 must havebeen due to the elasticity of the ribs 

 and their cartilages, together with that of the 

 lungs. By an arrangement, we could force in 

 different quantities of air, and measure the 

 collapsing power of the elastic parts, through 

 the medium of the confined air pressing upon 

 a column of mercury : the following was the 

 result : 



TABLE K. Costal clastic Collapse. 

 X H. 



Inch of 



cub. in. mercury. 



Air forced in 70 Resisting elasticity 1'20 



Ditto 90 ditto 1'25 



Ditto 160 ditto 2'50 



We could not force in more air, for with this 



pressure it was impossible to prevent the air 

 escaping with great rapidity through the ne- 

 cessary wounds. This experiment was re- 

 peated three times with the same result. It 

 will be remembered that X. H. had drawn 

 into his lungs, when alive, 75 cubic inches 

 of air more than we could force in, after 

 death. If, therefore, 160 cubic inches pro- 

 duced a collapsing elastic force equal to 2'5 

 we may suppose that 235 cubic inches would 

 produce an elastic force equal to not less 

 than 3'9 in. of mercury. This chest, mea- 

 suring 256 superficial square inches, it fol- 

 lows that X. H., in breathing out 235 cubic 

 inches of air, with no more sensible effort 

 than that of a mere sigh, had to overcome 

 with his inspiratory muscles a gross elas- 

 tic resistance of about 499lbs., and with a 

 force equal to this weight would the thoracic 

 walls recoil for expiration upon the air in his 

 lungs. 



N. C., height 5ft. 8in., weight lOst. lOlb., 

 set. 21: vital capacity, 200 cubic inches; ab- 

 solute capacity, 24-5 cubic inches; superficial 

 measurement of the entire thoracic cavity, 

 256 square inches ; circumference of the chest, 

 alive, 33 inches, dead, 34. Temperature of 

 the body, when examined, 97 F. Tempera- 

 ture of the air forced into the lungs, 63 F. 

 This man was what is termed " thick set," 

 firm, erect, and well built, a porter by trade, a 

 very different case from the former. The fol- 

 lowing was the elastic power of his ribs : 



TABLE L Costal Collapse in N. C. 



Inch of 

 cub. in. mercury. 



Air forced in 70 Resisting elasticity TOO 



Ditto 90 ditto 1-50 



Ditto 180 ditto 3'25 



Ditto 200 ditto 4'50 



The first ninety inches of air introduced 

 ruptured the lungs ; therefore the elasticity of 

 the lungs did not interfere with our experi- 

 ments. In both cases this resistance must be 

 referred only to the ribs, their cartilages and 

 ligamentous attachments ; also, in both cases, 

 the bodies were kept erect, or in the sitting 

 posture ; this should be attended to, for the 

 mere weight of the body upon the ribs when 

 recumbent would increase their collapsing 

 power. 



These tables express a dead power al- 

 ways in reserve, equally powerful whether 

 we are in robust health, or emaciated by 

 age or disease. Dead or alive, this is ready 

 to be put into force ; and, in fact, it is 

 never at rest, never at zero, until death ; we 

 may even go farther, and say, not until de- 

 composition has weakened the collapsing ten- 

 sion of these parts. Cut through a costal 

 cartilage, or take out a small portion of the 

 sternum, say corresponding to the 3rd, 4th, 

 and 5th intercostal spaces, and the opening by 

 the elasticity of parts will retract, and we 

 never can restore them again to their original 

 fit, because the thoracic parietes are still not 

 at rest. The bony cage-work of the chest is 



