the alternate repletion and depletion of the vessels, is an additional cause of irritation. It follows, therefore, that the treatment should always be medically supervised.

The researches of Speck seem to show that the method also produces a chemical action. The increase in the pulmonary aëration leads to an augmentation of the oxygen absorbed and of the carbonic dioxide eliminated. As far as the superoxidation of the blood is concerned, inspiration of compressed air acts in the same manner as respiration in the pneumatic chamber. The expiration into a rarefied atmosphere withdraws a considerable quantity of residual air, rich in CO2, and thus brings about a decarbonization of the blood, and consequently an antidyspnoeic effect.

Speck expresses the results that can be obtained by the following figures: Increase in air respired, 1:1.62; increase in oxygen absorbed, 1:1.14; increase in carbonic dioxide eliminated, 1:1.30. The same author has also demonstrated that the increased consumption of oxygen and elimination of carbon dioxide do not necessarily augment intra-organic oxidation.

Although all these effects are ultimately mechanical, depending upon the physical laws of the diffusion of gases, nevertheless the improved respiration which supervenes when the treatment is persisted in brings about an altered state which impresses the entire organism and stimulates the nutritive processes. Decisive researches are still wanting in regard to the question of nutritive effects.

As already stated, the combination most frequently resorted to is the inspiration of compressed air and the expiration into rarefied air. Two methods are in vogue-in the one, known as the intermittent method, the patient makes a series of inspirations of compressed air, the expiration being into ordinary atmosphere; then follows a series of expirations into rarefied air, inspiration taking place in the normal atmosphere.

The alternating method consists of an inspiration of compressed air followed by an expiration into rarefied air.

In these diverse combinations the mechanical effects do not counterbalance themselves, they alternate.

The lungs fill and empty themselves more completely, and pulmonary aëration is rendered as energetic as possible. It is this form of pulmonary gymnastics that exercises the most marked effect upon dyspnoea.

Furthermore, while the one factor in the method produces hyper

æmia of the lung, the other leads to anæmia. There is, therefore, not a continuous action, but an alternating one, which stimulates the pulmonary circulation.

Under these circumstances there need be but little fear of hemorrhages, as the effects upon the heart and circulation are less pronounced than in the case where only one of these practices is employed.

Therapeutic Application. The technique is quite simple. Various forms of masks and mouthpieces have been devised, but the best is a sort of trumpet, which is applied to the mouth. The patients should be instructed to breathe slowly and deeply; if desirable, the nostrils may be occluded.

In the beginning of the treatment the applications should be brief and should consist of a series of inspirations of compressed air, followed by expiration into ordinary air. Later, recourse may be had to the alternating method.

The duration of the treatment is variable; it can be prolonged without inconvenience. The spirometer and pneumotometer enable us to determine the exact results achieved.

In special cases the inspired air may be charged with medicinal substances; if necessary, its temperature may be modified and it may be impregnated with watery vapor.

As inspiration of compressed air diminishes the afflux of blood to the lungs, it may be considered as an antiphlogistic measure. It is chiefly indicated in the cases in a which predisposition to phthisis exists, and even in those in which the disease is already established. It favors the expansion of the lung after the subsidence of a pleurisy, and hastens the absorption of exudates. In addition, it is capable of causing the disappearance of atelectasis in bronchitis, and reestablishing the permeability of contracted and compressed bronchi; it also facilitates expectoration.

Expiration into rarefied air, since it determines a better evacuation of the accumulated air from the lung, is especially applicable in emphysema and in chronic bronchitis. Hence the alternating method is most useful.

All these methods of pulmonary gymnastics in general render most excellent service in cases in which the thorax is contracted and the respiratory muscles are enfeebled, conditions seen in persons of the "phthisical tendencies." Under these circumstances the treatment is eminently prophylactic.

It is also recommended in chlorosis and in other anæmias, and in dilatation of the heart. The results in these diseases are more doubtful.

Inspiration of compressed air is contraindicated in arterial atheroma, in the apoplectic habit, and in dropsy and venous stasis.

Cardiac weakness, the tendency to hæmoptysis, dilatation of the bronchi, the existence of acute inflammation of the respiratory apparatus, contraindicate expiration into rarefied air.

PART II.

CLIMATE.

WE come now to a consideration of a complex natural agent— climate-a potent resort in the treatment of disease.

By climate we understand the complexus of meteorological conditions to which a terrestrial place is subjected during the course of a year. From the medical standpoint climate is considered in its relations to and influence upon the life of organized beings.

Hygiene studies climate in its constituent elements and investigates the effects which it produces on the individual or the race, the causation of disease, and on mortality.

Therapeutics concerns itself with the influences which a change of climate has upon disease. So important are these influences that Michel Levy has uttered the dictum: "Change of climate is equivalent to rebirth.”

When life is menaced by a dangerous malady, or is liable to be so menaced by the later development of an incipient disease, the profound influence for good which a change of climate has upon the health should always be considered. Any action taken upon this consideration should be deliberate and should be founded upon an intimate knowledge of the climate selected, particularly of its therapeutic influence.

A few points, not directly germane to such knowledge, are of sufficient importance to warrant a brief consideration.

The transition from one climate to another should not be abrupt. It is important not to transport a patient from the cold frigid directly to the hot torrid zone. The facilities of the journey or of the voyage should also receive attention.

The place selected should possess satisfactory conditions, and should offer sufficient resources for the personal comfort of the patient. In certain cases a change of climate becomes therapeutically useful and enables the patient to return to his native country. This occurs in