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action of inspiration, the upper ribs alone rise, that the lower ribs descend 

 and slightly close on the chest, while the middle ribs project outwardly, 

 and that in expiration, the former set of ribs descend, that the latter start 

 a little outwardly, and that the middle set encroach on the cavity of the 

 chest. The learned Professor adds, that the cartilaginous articulating 

 surfaces, by which the ribs are connected to the transverse processes of 

 the vertebrae, appear to him to favour these different motions, as the di- 

 rection of the articulations of the upper ribs, is upward, and that of the low- 

 er downward; but on considering the subject with attention, it will be 

 seen, that the surfaces by which the transverse processes of the verte- 

 brae are articulated to the tuberosities of the ribs, are turned directly for- 

 ward in the greatest number, some of the lower ribs are, at the same 

 time, directed slightly upward. If we examine the action of the bones 

 of the chest, during inspiration, in a very thin person, for example, in 

 phthisical patients, whose bones are covered with little else than skin, we 

 shall find, that all the ribs rise, and are carried somewhat outwardly. It 

 is not easy to conceive how the intercostal muscles, which Professor Sa- 

 batier considers as the agents of respiration, should elevate the upper 

 ribs and depress the lower. The diaphragm, whose circumference is in- 

 serted in the latter, might, by its contraction, produce this effect; but as 

 the intercostals have their fixed point of action in the upper ribs, they 

 oppose and neutralize this effort, and all the ribs are elevated at once. 

 If this were not the case, the ribs ought to be depressed, whenever the 

 intercostals contract, since the lowermost, fixed by the diaphragm, would 

 become the xd point on which all others should move. 



As the fibres of the external and internal intercostal muscles, are in di- 

 rect opposition to each other, those of the former set of muscles having 

 an oblique direction, from above downward, and from behind forward, 

 and crossing the fibres of the other set whose obliquity is in a different di- 

 rection ; several physiologists have thought, that these muscles were op- 

 posed to each other, that the internal intercostal muscles brought toge- 

 ther the ribs, after they had been separated by the external intercostals, 

 the one set being muscles of expiration, while the other set contracted 

 during inspiration. 



It is well known with what pertinacity, Hamberger, in other respects, 

 a physiologist of considerable merit, defended this erroneous opinion, in 

 his dispute with Haller; it is now, however, ascertained, that all the in- 

 tercostal muscles concur in dilating the chest, and that they ought to be 

 ranked among the agents of inspiration, because the unequal capacity of 

 motion in the ribs, prevents the internal intercostals, the lower insertion 

 of which is nearer to the articulation of these bones to the vertebrae, from 

 depressing the upper ribs. Of the very conclusive experiments,by which 

 Haller undertook to refute the arguments of his adversary, I shall relate 

 only that which is performed by stripping the parietes of the chest, in a 

 living animal, of all the muscles which cover it, and by removing, in dif- 

 ferent pails of the thorax, some of the external intercostal muscles. The 

 internal intercostals are then seen to contract during inspiration, toge- 

 ther with the remaining external intercostals. These muscles, therefore, 

 have a common action, and are not in opposition to each other. The 

 same experiment serves to prove the increased dimensions of the space 

 between the ribs. On holding one's finger between two of the ribs, it 

 feels less confined, when during inspiration, these bones rise and thrust 

 forward the sternum. 



