expiration,—we may take it as a rule that in a penetrating wound of the chest the lung will sooner or later collapse, unless the inevitable consequences of the wound be happily arrested by treatment. This collapse will always be in a time proportionate to the relative size of the opening or openings. If the opening or openings be smaller than the glottis, the collapse will be slower; if larger, the collapse will be more rapid : and, in an imaginary increasing opening, the time will arrive when the collapse will be instantaneous. The openings caused by Minié balls are generally larger than the glottis; hence, doubtless, one great cause of the high rate of mortality, alike in the field as in the hospital, in cases of penetrating wounds of the chest.

CHAPTER V.

ON THE DIAGNOSIS AND PROGNOSIS OF PENETRATING

WOUNDS OF THE CHEST (CONTINUED).

The theory of Dr. Hoadley is ingeniously explained by a drawing of a machine, accompanying his Lectures. The machine consists of two square boxes of equal size, divided by a partition. The two boxes represent the pleural cavities; the partition represents the mediastinum. To the inside of the top of each box is attached a bladder. The two boxes are connected together by means of a tube on the outside, to the centre of which is attached another tube. This tube represents the trachea. The two diverging tubes which lead into the bladders consequently represent the chief bronchus of each lung; and the bladders the left and right lung respectively. These tubes are fitted with stopcocks, so that the bladders can be inflated and emptied at pleasure. In the lower side or bottom of each box is a round aperture, furnished with a rim, to which is suspended a large cylindrical bladder, having a free communication with

the air contained in the boxes. The whole apparatus being air tight, it will be evident that, by alternately compressing and relaxing the outer cylindrical bladders, an action similar to the motion of the lungs and costal walls during respiration will be produced. Apertures are formed also at the end of each box, also in the partition, and each aperture is provided with a revolving metal plate, constructed to regulate the admission of air; by this additional arrangement, it is easy to observe the counterpart action of the lungs when respiration is disturbed by the effects of perforations in one, or both sides of the thorax, or through the mediastinum.

A more simple, but not the less illustrative, apparatus may be formed by a pair of bellows. We have only to suppose the chamber of the bellows to be divided into two compartments, and each chamber provided with a bladder. The nozzle, made to communicate separately with each bladder, will represent the trachea. By alternately raising and depressing the handle, the full action of respiration will be imitated. By this simple contrivance the appearance of collapse of the lung or lungs, also of emphysema, also of the curious fact of the lungs expanding when the thorax contracts, and the lungs collapsing when the thorax expands, after a wound in the chest, may be plainly demonstrated.

The experiment No. 3, page 29, fully cor

roborates the occurrence of this phenomenon; but, on the other hand, experiment No. 8, page 39, tends to weaken the evidence in favour of Halliday's explanation: for admitting that, in this experiment, “a spasm of the glottis” was present, the question arises, Whence came the gas or air which inflated the right lung ? seeing that the left lung was contracted, bound down, and disqualified to fulfil the necessary conditions; although it may be admitted that, even in a collapsed lung, a sufficient amount of air will enter to cause the protrusion.

I was unable to verify, in the numerous cases which came before me, the very remarkable fact, that when an opening, at least equal to, or larger, than the glottis, is made into the thorax, the lung, in the wounded side, expands on expiration, and contracts on inspiration, but this fact was proved most clearly in two experiments, No. 7, page 34, and in No. 8, as follows.

Experiment 8. An opening made, one inch and a quarter in diameter, between the fourth and fifth ribs, into the right thoracic cavity of a healthy dog, avoided wounding the lung, but brought it fully into view. It was now distinctly seen to approach the aperture upon the act of expiration. Made a similar opening into the left pleural cavity.

This cavity was found filled with a yellow-coloured serum, which flowed out, and the lung was seen contracted, and bound down to the spine. The right lung was found to be perfectly healthy.

Having considered, from the state of the lung, that no further valid observation on our present subject could be made, we turned our attention to the heart.

We observed that the systole of the heart was sequential to inspiration. Upon the application of ammonia to the nostrils, the languid action of the heart was instantly increased both in strength and number; but the number of respirations remained the same. On passing the finger behind the heart, its impulse was felt equally on all sides, clearly showing that it is no “ tilting up” which causes the external impulse. The cardiac action endured for an hour and a half after the animal had lost sensation.

It may be inferred, therefore, that in all the cases in which air passed through the wound, as it invariably occurred during the act of expiration, at that moment the lung, although unseen, did rise towards the aperture. See table, page 52, cases Nos. 2, 7, 11, 12, 14, 16, 30.

In Nos. 2 and 7, the lungs were wounded. In Nos. 11, 12, 14, 16, and 30, the lungs were not wounded. No reliable practical deduction can, therefore, I am sorry to say, so far at least as my cases go, be drawn from this very curious physiological fact.

Dr. Houston explains this phenomenon by referring it to the sudden diminution of the lower part of the cavity of the chest, occasioned by the strong