In many industrial pursuits the lungs are subjected to extreme pressure or strain by which they are brought into a state of or ganic disease. Glass-blowers afford a common illustration of this class of injury. In their occupation, while blowing glass during the time it is in the molten state, their lungs, which are for the moment the blowers, are subjected to extreme strain. The deep inflation of the lung produces, after a time, extensive dilatation of the minute air tubes. The dilatation passes into permanent enlargement, and in workmen of not very advanced years is fol lowed by rupture of the air vesicles, emphysema. When this accident occurs two sets of evils are established. The first is shortness of breath, because a portion of the lung is disabled, and the air in it is not duly expelled by the natural elastic contraction; in plain words, the lung is not efficiently filled and emptied. In the second place there is a deficient oxidation of the blood; a large volume of air taken into the lungs is not made available for respiratory purposes.
Under the influence of these two changes the person, who is affected by them suffers from shortness of breath, paleness, cold ness of the surface of the body, dyspepsia attended with consid erable flatulency, debility, and comparatively early disablement. Persons so affected are also exceedingly liable to danger from accidental bronchial complications, such as bronchitis from cold or exposure to some other exhausting or debilitating cause.
Other classes of men than glass-blowers suffer in like manner from pressure upon the pulmonary structure. I notice among these, particularly, the workmen called paviors, who while en gaged in laying stones use the heavy maul or instrument called the rammer, which they lift up about half a foot from the ground, and then let fall upon the paved surface. From a curious habit these men as they let the rammer descend jerk out the air from their chests with a noisy effort, and then draw in a very deep breath. By this absurd process they produce dryness of the throat, hoarseness, a sense of exhaustion in the muscles of the chest, and a feeling of emptiness within the chest. After a few years the constant mechanical strain leads to dilatation of the bronchial tubes, rupture of the air vessels, and emphysema. The lives of these men are usually precarious and short.
Playing upon musical wind instruments is sometimes a cause of disease of the lungs, owing to the pressure which is maintained during long retention of the breath after deep inflation. It has been stated that players on wind instruments are less susceptible to severe forms of chest disease than are other persons. I can find 110 precise data to support this view, although it may be that those who are disposed to consumption of the lungs are benefited by any act which, in moderation, causes regular and deep inspira tion. When I first commenced professional life, there was a physician living in London who made considerable reputation by the invention of what was commonly called a whistle or blow tube, through which consumptive persons were taught to breathe deeply several times a day. It would seem that some good was really effected by this plan, and it is told of Cuvier, the great naturalist, that he, being threatened with consumption in his youth, was greatly benefited from reading aloud every day, by which the lungs were freely exercised and filled with air.
I think I have seen, for the same reason, some benefit from playing very moderately on a wind instrument. On the other when such playing becomes a professed occupation, and the player is for many hours a day subject to over-distention of the lung, the delicate pulmonary structure is very soon apt to lose its elasticity and to become emphysematous. Bassoon, trombone, horn, and trumpet players are specially liable to these injuries, although the liability is not equally distributed amongst them. An intelligent bandmaster once explained to me why some suffer soon and others escape. It depends, he said, on the question whether the player has or has not learned the art of retaining a large volume of air in the mouth and throat, and of charging the distended parts from the nostrils while still playing. Some learn this art so well it becomes with them an unconscious act, and their lungs are scarcely at all influenced. Others make a distended lung the reservoir, and, in fact, hold their breath all the time they are playing. It is these players who break down.
From holding the breath very closely in playing a wind instru ment, the circulation through the lungs is sometimes impeded, and pressure of blood is thereby thrown on the right side of the heart. An amateur flute-player, whose history came under my observation, suffered from a very singular accident in this way. From the tension of holding his breath the right side of his heart was engorged, and the membrane which closes the foramen ovale or festal opening between the two auricles gave way. He became, thereupon, of dark color all over the body, cold, and subject to that form of disease described at page 136 as cyanosis, or blue skin disease.
In other instances the obstruction to the flow of blood on the right side of the heart during the process of playing prevents the due return of blood by the veins from the head, and leads to pressure of blood upon the brain with vertigo and nausea. I knew this to occur, in the case of an amateur clarionet-player, to such an extent that lie was obliged to give up the practice. In youths who have been trained to hand exercise one or other of the above named symptoms is not 'Infrequently met with, and is an indica tion that the constitutional peculiarities are against the prosecu tion of the art.
Another curious disease from pressure is called Caisson," or " Coffer-dam," disease. It belongs to an industry that is practi cally of modern introduction, and is brought about by the process of subjecting the body to great atmospheric pressure and after wards suddenly relieving it from the pressure.
In laying piles of bridges and in some other similar works it is necessary to place the workmen in enclosed spaces beneath the level of the water, and to exclude the entrance of water by forcing air into the spaces in which the work is carried on. These en closed spaces, or rather the tubes which form the enclosures, are called "caissons," or coffer-dams. In them the compressed at mosphere in which the workmen labor is confined, and to the diseased conditions which result in the men the term " Caisson disease " is applied.
The ordinary pressure of the atmosphere on man is fifteen pounds to the square inch of surface of the body. Under that pressure all the functions of life are naturally carried on. In the caisson the air is pumped in with such force that an addition of two, three, and even four atmospheres may be maintained, under which additional pressure the workmen have to follow their avo cation. If a workman can work ten hours under the ordinary pressure of one atmosphere, he can work five hours, or half the time, under two atmospheres, three hours and twenty minutes, or a third of the time, under three atmospheres, and two hours and a half, or a fourth of the time, under four atmospheres.
It was soon detected that when work was prosecuted under these pressures, some peculiar physiological changes were pro duced in the workers. It was observed that the blood in their veins became of the same red color as that in the arteries, that the breathing was quickened, that the action of the skin was profuse, and that when the men returned from their work to the ordinary atmospheric pressure they were subject to pains in their limbs, and to giddiness, with other symptoms of nervous disturbance.
The caisson disease has recently been most carefully studied by Dr. Andrew H. Smith of New York. Dr. Smith, whom I have the pleasure to know, has had an unexampled experience of the disease afforded to him while attending numbers of caisson laborers at a great work which has recently been carried out near to New York. The disease, he says, depends upon increased at mospheric pressure, but is always developed after the pressure is removed. It is characterized by extreme pain in one or more of the extremities, and sometimes in the trunk of the body, and this pain may or may not be associated with pain in the stomach and vomiting. In some cases the pain is accompanied by paralysis, more or less complete. The paralysis may be general or local, but is most frequently confined to the lower half of the body. Head ache and vertigo are sometimes present. The above symptoms are connected, at least in the fatal cases, with congestion of the brain and spinal cord, often resulting in effusion of serum or of blood, with congestion of one or more of the abdominal organs. When sufficient time elapses before death there may even be soft ening of the brain in parts of that organ.
The one essential cause of the caisson disease, according to Dr. Smith, is the transition to the natural atmospheric pressure after a prolonged sojourn in a highly-condensed atmosphere. Without this change the disease is never developed, and in some workers it is never developed at all, so that a special predisposition to it seems necessary.
The study of the caisson disease has led Dr. Smith to the opinion that it affords a key to the singular though very common predisposition to pains in the limbs on the approach of a storm. These pains are generally considered to be of a neuralgiac charac ter, and to depend upon the dampness of the atmosphere. But, as the caisson disease affords examples of precisely the same pains, immensely intensified in degree, and resulting from the diminu tion of an atmospheric pressure to which the body had adapted itself, irrespective of any question of humidity, analogy suggests that the so-called neuralgiac cases are simply exaggerations of a predisposition identical in kind with the one under discussion, and produced, not by the influence of moisture, but by the low barome tric condition of the atmosphere which precedes a storm. It is true that the change in time pressure is insignificant when compared with that which produces the caisson disease, but it is supple mented by the longer duration of the higher pressure to which the subject has been previously exposed.