expand the upper portion of the lower lobe, and, on the descent of it, the lower portion of the upper lobe.

The division of the ribs into the three sets of thoracic, diaphragmatic, and intermediate, which I proposed on anatomical grounds, I find of practical value in the diagnosis of disease, as I shall have to state more fully hereafter. The important practical point to bear in mind with regard to the respiratory movement of the different sets of ribs is, the portion of lung that each set expands.

During a deep inspiration, the anterior portions of the ribs. move forwards and upwards, and through the intervention of their cartilages carry forwards and upwards the sternum; while the posterior portions of the ribs move backwards, and push backwards the dorsal column.

The dorsal vertebræ form an arch, and as the ribs of the intermediate set, the sixth, seventh and eighth, are longer than those of the thoracic set, they thrust backwards the middle of the dorsal arch further than those of the thoracic set push backwards the upper part of the arch; the dorsal arch is consequently deepened, and, therefore, shortened.

The shortening of the dorsal arch, and consequent lowering of the head, during each involuntary inspiration, is very manifest to the eye in persons, especially in females, lying on the side, suffering from dyspnoea.*

Dr. Hutchinson says (Med.-Chir. Transactions, vol. xxix. p. 191), "The head is protruded and lowered in the deep expiration," "raised and thrown back in the deep inspiration." I am satisfied that this is accurate as applied to those he observed, who were examined when erect, and who were desired to expire and inspire deeply; as they were erect the straightening and lengthening of the lumbar curve counteracted the deepening and shortening of the dorsal curve. Besides this, their breathing was voluntary. They elevated the head with one set of muscles, while they expanded the chest with another. One thing is certain, that in the erect posture, although healthy men usually raise the head when they take a deep voluntary inspiration; yet women in tight stays, whose breathing is markedly costal, and persons affected with emphysema, lower their heads when they inspire involuntarily to the extent of 01 to 02 in. When I take a deep inspiration, I can either elevate the head 50 in. or lower it 40 in., or keep it perfectly still, so much

Each of the four or five superior ribs (the thoracic set) ascends during inspiration more than the rib above it; they consequently then move nearer to each other; while the diaphragmatic and intermediate ribs move further apart. This, as I have shown in my paper on the Mechanism of Respiration, is in great part due to the articulation of the ribs with a moveable dorsal arch.*

control has will over the movements of respiration. In the tranquil breathing of men, the shortening of the dorsal arch is imperceptible, their costal respiration being so trifling; but in females, it may usually be observed. It follows from these observations, which can be readily verified, that Dr. Hutchinson's remark, that "The body is lowered or shortened in expiration," must be qualified; as in the instances I have mentioned, the body was then markedly lengthened. During voluntary deep expiration, and during the act of coughing, the body is markedly shortened, as then the powerful abdominal muscles pull downwards and forwards the sternum and ribs, and, through them, bend forward the lumbar vertebræ.

* Dr. Hutchinson says, p. 215, "In inspiration the ribs diverge from each other, in expiration they converge towards each other." This statement, correct as regards reptiles and birds, requires to be qualified in regard to man, and the mammalia who possess, like man, a dorsal arch. It may be easily observed on a thin person by placing one finger on the third and another on the first rib, that they converge during inspiration, while, by adopting the same plan, from the seventh to the twelfth, it will be found that they diverge. The divergence of the diaphragmatic ribs is very great, and it is in part owing to their great divergence that the action of the middle parts of the tenth and eleventh external intercostals is expiratory ; while it is owing to the great convergence of the upper ribs that the internal intercostals between the first and the third ribs are inspiratory, thus reversing in each instance the natural action of those muscles, the former of which is in the bird and reptile throughout inspiratory, and the latter throughout expiratory. I beg to refer on this interesting subject to the plates and description in the paper on the Mechanism of Respiration.

Postscript, August 1848.-It is interesting to notice that these views, which I hope to have an early opportunity of demonstrating, account for and reconcile the different views of the action of the intercostals, held by the great physiologists of the last century, who occupied themselves so warmly in what may be termed the battle of the intercostals.

Hamberger constructed a machine representing the sternum, the vertebræ, and two ribs, with threads interposed to imitate the external and internal intercostals and the inter-cartilaginous muscles. From this he inferred that the external intercostals are all inspiratory-the internal

While the thoracic set of ribs approach each other, their cartilages ascend and the inter-cartilaginous portions of their internal intercostal muscles act during inspiration.*

all expiratory, and that the inter-cartilaginous muscles are inspiratory. -(Haller de Respiratione. Opuscula Anatomica, pp. 50. 92.)

Of this machine, Haller says, "Ponit nimirum CL. AUCTOR machinæ suæ costam utramque æque mobilem esse. Sed hujus modicostas DEUS nobis non dedit."

In opposition to Hamberger, Haller observed that he had overlooked, among other things, the difference of mobility in different ribs-the second rib being five times more moveable than the first, and so on; and he showed, from experiment, that during extreme inspiration the space between the first and second ribs diminished from 85 in. to 63 in.; and on extreme expiration it again increased from 63 to 89 (p. 52). He also showed that the ribs rotated on themselves, the lower edge moving outwards (p. 126). That the external intercostal and the inter-cartilaginous muscles were inspiratory, he agreed with Hamberger; but he differed altogether with regard to the internal intercostals, which he observed to be inspiratory in the superior intercostal spaces, especially in the first, in many experiments carefully conducted. He noticed that, below, the internal intercostals scarcely acted; but he laid it down as a rule that the internal and external intercostals combine to expand the chest during inspiration, thus agreeing with Mayow.

In this controversy both were right and both were wrong. Each was right in what he observed; but he did not observe the whole of the complex respiratory apparatus. Hamberger was right as to the lower ribs, for they diverge during inspiration. Haller as to the upper ribs, for they then converge. Hamberger, with Bayle, Fabricius, and Hoadley, was right in part, as to the separate functions of the outer and inner intercostals, the external being inspiratory, the internal expiratory throughout, behind and between the intermediate and adjoining ribs, at the side in man and the other mammalia, and throughout in reptiles. Haller was right in stating that the internal and external intercostals acted together in the upper intercostal spaces.

Dr. Reid, in an admirable article on respiration (Cyclopædia of Anatomy and Physiology, vol. iv. p. 333), says, the two lower ribs descend during inspiration. I observe that the lowest is stationary, the eleventh ascends, and both move backwards. From this relative motion of the two lowest ribs, whether on Dr. Reid's view or mine, the lowest external intercostal must be expiratory.

I imagine that Dr. Hutchinson's machine (which is like diagrams in Hoadley's, Bernoulli's and Monroe's works, and in my own paper) resembles Hamberger's, and that, like Hamberger, in acknowledging partial truth he has been led into partial error.

"The cartilaginous portions" " of the second, third, fourth, and fifth

The movements that take place during a deep inspiration are these:-the scapulæ are raised; the anterior portions of the ribs, the sternum and the clavicles move forwards; the posterior portions of the ribs and the dorsal and lumbar vertebræ move backwards; the sternum and the dorsal arch become, both of them, more curved; the third, fourth and fifth costal cartilages at each side of the sternum advance more than the sternum, and the anterior prominences formed by those cartilages become fuller; the angles of the ribs move backwards more than the spine, and the deep space formed for the lung to each side of the spine increases in depth; the ribs expand laterally to a great but varying extent, the diaphragm descends, and the abdomen protrudes considerably, often more than an inch.

These movements of thoracic expansion are necessarily attended by the expansion and descent of the lungs and heart, and the compression and descent of the liver, spleen and stomach, and all the abdominal and pelvic viscera.

The lungs of course spread wherever the space is increased for them. The bulk of the upper portions of the lungs is in front, and of the lower portions behind; and, in conformity with this arrangement, the inspiratory movements of the superior ribs, or the thoracic set, is chiefly forwards and upwards, while that of the inferior or diaphragmatic set is chiefly backwards, (see the dotted lines in the figure at page 364, which indicate the thoracic expansion anteriorly and posteriorly,) the lower ribs not ascending so much as the upper, and the lowest of all having scarcely any ascending motion.

The diaphragm, in its descent during a deep inspiration, first flattens its own convexity, especially on the right side, and then descends from an inch to an inch and a half. It, consequently, lessens the concavity at the base of each lung,

ribs" "are, during inspiration, raised and brought nearer to each other by the contraction of the sternal and inter-cartilaginous portions of the deep intercostal muscles."-The Author, on the Changes in the Situation of the Internal Organs. Provincial Medical Trans., vol. xii. p. 354.

especially the right, and draws down the whole base of each lung; in front, the right base descends from the lower end of the sternum to the lower end of the xyphoid cartilage, and both bases descend from the sixth costal cartilages to the seventh. At the side and behind, the descent is in the same proportion. The contraction of the central muscular fibres of the diaphragm draws down its central tendon from three-quarters of an inch to an inch. The heart is necessarily drawn downwards to the same extent; while the lungs spread into the space previously occupied by the heart, and cover it to an increased extent, so that the exposed portion of it is diminished. The heart is now shielded by the left lung at the fourth and fifth intercostal spaces, and its impulse is no longer felt there, but it is felt, instead, behind, below, and to the left of, the xyphoid cartilage.

While the descent of the diaphragm lengthens the thorax it compresses the abdomen. The liver, stomach, spleen, pancreas, kidneys, and all the abdominal organs, the uterus (the inspiratory descent of which has been felt by Dr. Frederick Bird), and all the pelvic viscera, are pushed downwards during a deep inspiration; at which time the perinæum protrudes more than it does in the tranquil state.

These inspiratory movements of the diaphragm have doubtless an important physiological action on the abdominal organs in thus displacing and compressing them. The blood, which accumulates during expiration in the solid viscera, is, during inspiration, drawn off, and the hollow viscera have their innate contractile force assisted.*

Dr. Hutchinson says, op. cit., p. 187, "It appears to me a matter of doubt whether the diaphragm in the act of inspiration descends at all." This doubt has arisen from the falling in of a part of the abdomen during voluntary deep inspiration in the erect posture. In healthy persons when recumbent the abdomen between the xyphoid cartilage and the umbilicus moves forward, during an ordinary inspiration, 3 in., and during a deep inspiration from 5 in. to 1.5 in.

Any one may readily prove to himself the extensive descent of the diaphragm during a deep inspiration. Percuss over the lower margin of the right lung, ascertain its boundary, and mark it; desire the person to