This old malady becomes more rare as we approach the higher latitudes. It is supposed not to exist at all in Siberia, in Iceland, and in the Faroe Islands. Thus, diseases of the lungs seem to be more rare in certain cold countries than in warm countries. It is also observed that at a certain altitude the number of cases greatly diminish, and even completely disappear. Brockman testifies that phthisis is rare on the plateaux of the Hartz mountains at the height of two thousand feet above the level of the sea; and C. Fuchs, stating the same fact concerning certain elevations in Thuringia and the Black Forest, was the first to advance the theory that phthisis diminishes according to certain altitudes. Dr. Brüggens, also, has since testified to the infrequency of this disease in the Swiss Alps, at the height of 4500 to 6000 feet in the Engaddine; nor is it found among the monks of the Great Saint Bernard at the altitude of 6825 feet. According to M. Lombard, it completely disappears among these mountains at the height of 4500 feet. The populous cities of the American continent, which are situated in the tropical zone at an altitude of six thousand feet above the level of the sea, are exempt from lung diseases; although, in the same latitude, phthisis is common in lower regions, This immunity exists on the other hemisphere in the same zone--on the elevated plateaux of Hindostan and the Himalaya. In examining the state of the climate on the heights in which phthisis is seldom or never found, we find there, even on the equator, a medium temperature sufficiently low throughout the year; between twelve and fifteen degrees on the heights below 9000 feet; between three and five degrees on those between 9000 and 12,000 feet. In the temperate zone it is still lower. But the warmest months upon tropical heights do not vary more than six or eight degrees from the medium temperature. It is the same on the plateaux of the Alps and in Iceland, and is a general and common characteristic of the regions in which phthisis is not found. The deviations below the annual medium, appear even to increase this immunity. If sufficient observations have not been made to decide upon the degree of comparative humidity on the heights above 12,000 feet, we know that the elevation at which phthisis is wanting, is in a hygrometrical condition more nearly approaching saturation than the lower regions, and that the rains are also more abundant there. It is desirable that the heights of Cévennes, the Pyrenees, the Alps, and, above all, the elevated parts of our Algerian possessions should be carefully studied, with a view to the treatment of lung diseases, which are the great scourge of the human race, and which annually cause the death of more than three millions of its number.