However, the vision of these men is nearing fulfillment more and more as each year passes; 1925 brought the Air Mail Act, giving a definite solid incentive to the production and operation of a more economically correct airplane than the past had ever justified. Owing largely to the interest of the United States Navy, a really revolutionary change in the whole field of airplane design and use was made possible by the production of the air-cooled engine, and really sound and profitable air transport came within general reach for the first time in history.

It is of interest to note that the great American name of Wright was again the leader in this development, the Wright "Whirlwind" engine being the first air-cooled engine which proved sufficiently light and reliable to permit of the economically sound operation of aircraft. From this time onwards the pay load per horse power of the heavier-than-air machine became a factor around which serious budgets could be made, instead of somewhat of a joke to those versed in the business aspect of transportation.

From a figure of one pound per horse power, we were at once enabled to consider three, to even six pounds, and this latter figure does not represent the optimum-it is perfectly feasible today to build a comparatively slow freight-carrying airplane with a pay load of eight pounds per horse power, but the volume of business regularly obtainable for this type is not yet sufficient to create the demand for the vehicle. In this connection, there is still much discussion as to the economic value of this relatively high pay load, obtained as it is by the sacrifice of high speeds, in the light of our present knowledge. In general, the basic rule of all transportation activity is to carry the maximum load for the power used, but there are exceptions to this rule even in the older forms of transport-extra-fare trains, high speed motor busses and crack Atlantic passenger liners are examples. We are thus in the air transport industry today in the throes of argument as to whether really high speed is required by the business community at a correspondingly high price, or whether we

must carry larger loads at the lower speeds. Until very recently, there was little serious divergence of opinion as to the greater value of the increased pay load, but the developments of the last few months seem to indicate that higher speeds are more profitable ultimately, and that the really large load carrying capacity is the function of the lighterthan-air dirigible.

If this is eventually proved true, it is fairly safe to prophesy that the future of the airplane is in high-speed transportation at upwards of two hundred miles per hour over comparatively short stages, and that long journeys, such as the Atlantic and Pacific crossings, New York to South America, England to Australia, etc., will be done by the dirigible.

This conclusion is, I believe, the most logical that can be drawn from our past experience, and we can with confidence await the day when the earth will be encircled by giant dirigibles traveling at a little over one hundred miles per hour, stopping only at twenty-five hundred mile intervals, and being supplied with passengers from short airplane feeder lines with a two hundred mile per hour schedule over distances of some fifteen hundred miles.

TISSUE RESPIRATION AS THE FUNCTION OF THE INTERNAL SECRETIONS WHICH SCIENCE

HAS SANCTIONED

By CHARLES E. de M. SAJOUS

(Read April 21, 1928)

AN ALL-IMPORTANT feature of general biology-one very costly in human lives in medicine is well expressed by W. H. Howell, professor of physiology in John Hopkins when he states that "the respiratory history of oxygen ceases after this element has reached the tissues." This means that although oxygen was discovered by Lavoisier in 1771-80 and has since been traced to all tissues, its rôle therein has remained unknown. Personal labors, started in 1888 and continued ever since, have imposed the conclusion that both pulmonary and tissue respiration are carried on by the ductless glands, and that they are the only fundamental functions of these organs that science has sanctioned since I first formulated them in 1903.2

The internal secretions are now being developed in three main directions: the physiologic, initiated by Claude Bernard in 1848, who introduced the term "internal secretions"; the clinical, inaugurated by Addison in 1849; and the therapeutic, which, though traceable back over three thousand years to India, was placed on its modern footing by BrownSéquard in 1889.

In general practice, the trend has been to follow the lead of Brown-Séquard. The remarkable effects of testicular fluids upon his own organism, which effects I had occasion

1 Howell, W. H.: "Text-Book of Physiology," 10th ed., 1927, p. 915.

2 Sajous, C. E. de M.: "Internal Secretions and the Principles of Medicine,” 1903, 1st ed., pp. 120-128 and 801-850. Same in 2d ed., 1907, and 3d ed., 1909. In 4th ed., 1911; 5th ed., 1912; 6th ed., 1914; 7th ed., 1916; 8th ed., 1919; and 9th ed., 1921, pp. 56-70 and 801-850. In 10th ed., 1922, pp. 2-8, 59-71 and 801-850. Also, Gaz. d. hôp. (Par.), 1907, 80, p. 1407; Practitioner (Lond.), 1915, 94, p. 179; Endocrinology, 1917, 1, p. 4; ibid., 1922, 6, p. 197.

to witness, constituted a legitimate foundation for the use of extracts of the various ductless glands in practice and they were tried in all classes of disease with excellent effects in many, and either moderate or no beneficial results in others. Moreover, I have called attention to various conditions in which their use in practice might prove harmful. The rational or scientific use of these powerful agents could only be placed on a sound foundation by adequate knowledge of their fundamental mode of action. The same need is quite as applicable, however, to every phase of clinical medicine, pathogenesis, pathology, symptomatology, etc.

Unfortunately, and despite a large aggregate of invaluable contributions to our knowledge on the subject, the tendency is persistently to assert that the functions of these organs are unknown.

The purpose of this paper is to show that this discouraging attitude is groundless and that it is due mainly to the fact that no single branch of Medicine, pure or applied, can solve so far-reaching a problem. It required, to do so, the broader knowledge that co-ordination, analysis and synthesis of all branches at all relevant to the subject could furnish—a mode of research now termed "synthesis of sciences."

It was adopted over thirty years ago as the basis of my own researches on the ductless glands-studded, here and there, I may add, with experimental investigations needed to elucidate any mooted question which the research brought to light. A few details are necessary here to illustrate its bearing upon Medicine as a whole.

In 1902, after editing twenty-five volumes of my Annual of the Universal Medical Sciences, I became convinced that although some departments of Medicine were advancing at giant's strides, gaps existed on all sides which prevented the development of clinical medicine on rational lines. Symptoms, etiology, pathology and treatment were described with exceeding care, but the relations of cause to effect, that is to say the manner in which the lesions were produced or the symptoms were evoked by them, or the processes through Sajous, C. E. de M.: Virginia Med. Semi-Monthly, 1910, 14, p. 561.