tion of a foreign protein into the body, the sensitization of the body cells to that protein, and finally the cleavage of that protein by the ferment elaborated by the sensitized body cells. Now in nature practically all the proteins that find their way into the body undigested are living proteins, in the form of bacteria or protozoa. They grow and multiply in the body, without materially disturbing for the time being, the life of the individual. This continues during the period of incubation but when the body cells have become sensitized and begin to split up the foreign protein the period of incubation ceases and that of disease begins.

We have shown that repeated injections of foreign protein not only cause fevers of various kinds, but lead to emaciation of the animal body, to increased elimination of nitrogen, and to decreased urinary secretion, and, in short, to all the phenomena that are characteristic of the febrile diseases: Death from any of the infectious diseases is due to one and the same poison, and that poison is a constituent of the protein molecule. Symptoms vary in different diseases for two reasons: In the first place, the foreign proteins have different predilection places in the body in which they are deposited. In the second place the ferment which splits up these foreign proteins is specific for different diseases. The most successful diagnostician cannot determine the nature of the bacterial organism which causes the symptoms of meningitis. The symptoms are the same so long as the organ involved is the same. The meningitis may be due to the meningococcus, to the streptococcus, to the typhoid bacillus, or to the tubercle bacillus. Still, the symptoms are the same because the cleavage of the foreign molecule occurs in the same part of the body. Again, every medical man knows how difficult it is to distinguish between typhoid fever and acute general miliary tuberculosis, because in both instances the foreign protein is largely in the blood current. As I have stated, most bacterial proteins have predilection places in which they are deposited. The typhoid bacillus prefers the mesenteric and other glands; the pneumococcus is deposited generally in the lungs, though it may be found in the intestinal walls. The meningococcus finds its favorite place for growth and development in the coverings of the brain. The tubercle bacil

lus grows most frequently in the lungs, though it has fed upon man for so long a time that it is now able to sustain itself in almost any part of his body.

From what has been said it must follow that fever on the whole is a beneficent process. It is one of the phenomena of the parenteral digestion of proteins. The foreign protein has gotten into the body, is growing and multiplying, and in doing so is utilizing the proteins of man's body. It must be destroyed, and the body cells pour out a ferment which digests the foreign protein. This is nature's way of disposing of the foreign material, and it is apparently about the only way that nature has of doing it. I repeat therefore that fever on the whole is a beneficent process. It is an attempt on the part of nature to get rid of the invading protein. Like many other of nature's processes it may be overdone, and death may result from fever, per se.

That fever does result from a fermentative cleavage is shown not only by the facts which I have already enumerated, but those which we have learned in combating fever. Nearly all, if not all, of the anti-febrile reagents which have been employed in medicine are anti-ferments, and they lower the temperature by retarding the process of protein cleavage. Both natural and acquired immunity, apart from toxic immunity, may be explained by the facts as stated above. In natural immunity the foreign protein is either unable to grow and multiply, and this means that its ferments are unable to split up the proteins of the body, or the ferments of the body split up the invading protein before it has time to grow and multiply. This explains natural immunity, whether it be racial or individual.

Acquired immunity is explained by the fact that the first attack of the disease, or inoculation with a modified virus, develops in the body cells a ferment which is stored up, and which on a second injection of the same protein, acts rapidly, and effectively, and splits up the invading virus. In vaccination for smallpox we use a virus modified by its passage through the cow. This modified smallpox virus develops in the body cells a ferment which is capable of splitting up the smallpox virus, and the next time this individual comes in contact with a smallpox patient, or receives the smallpox virus, it is split up and destroyed before it has time to grow and multiply.

This also explains the beneficial effects that undoubtedly have been obtained by the various vaccines now so widely and often so unintelligently used.

I wish to suggest that the exanthematous diseases may be explained by the fact that the foreign proteins of certain diseases are deposited in the skin, and that this tissue is the site of the destruction of the foreign body. I may say in support of this that we have repeatedly injected egg-white into the ear vein of rabbits. After varying periods of time we have shown by sensitizing animals with blood taken from the heart that the egg-white has wholly disappeared from the circulating blood of the rabbit. Later it can be shown that this egg-white has been deposited in the skin, in the kidney, in the brain, and in various other organs of the rabbit. It seems to me that our work upon the protein poison furnishes us with facts, by means of which we are able to explain many of the phenomena of immunity and of disease.

SOME GEOCHEMICAL STATISTICS.1

BY FRANK WIGGLESWORTH CLARKE.

(Read April 20, 1912.)

More than twenty years ago, in a paper on the relative abun dance of the chemical elements, the present writer compared a number of averages of analyses of igneous rocks, representing different regions, and showed that they were essentially identical. From these averages, combined into a general average, the mean composition of the igneous part of the lithosphere was computed, and the result obtained has since been confirmed by the study of much larger masses of data than were originally attainable. Other estimates, made by other computers upon similar lines, have since served to check my own, thereby giving to my conclusions a high degree of probability. The figures obtained have received a fairly general acceptance, and have served as a basis for other computations of a fundamental character.

This acceptance, however, has not been universal. The process of averaging analyses is criticized by several writers, who urge that it is unphilosophical. An analysis of a dike rock is given the same weight as that of a widespread and important formation, whereas each rock should be weighted in accordance with its volume. But we do not and probably cannot know these volumes, partly because detailed surveys are lacking, and partly because a surface outcrop fails to tell us what bulk of rock may lie below. If we try to estimate the volumes of the many rocks represented in the average, or

2

1 Published by permission of the Director of the U. S. Geological Survey. Bull. Phil. Soc. Washington, 1889, Vol. 11, p. 131. Also in Bull. 78, U. S. Geological Survey, 1891, p. 34.

3

See Bull. 491, U. S. Geological Survey, "The Data of Geochemistry," pp. 22-27.

4

See, for example, Daly, Proc. Amer. Acad., 1910, Vol. 45, p. 211; Loewinson-Lessing, Geol. Mag., 1911, p. 248; and Mennell, Geol. Mag., 1904, p. 263, and 1909, p. 212.

even the areas exposed, we shall find ourselves relying in great part upon arbitrary assumptions, a procedure fully as unphilosophical as that which it would supplant. Estimates of that and similar kinds have been made, most recently by Loewinson-Lessing, whose figures give essentially the same result as that obtained by the method he has criticized. The method by volumes is doubtless ideal, but impracticable; and the true, philosophical procedure is to do the best we can with the available data. It is highly probable that the rocks of minor importance will balance one another, the persilicic and subsilicic varieties occurring in something like equal proportions. This supposition is sustained by the groups of average analyses which will presently be given. If we trust to individual judgments, different observers will reach widely different conclusions. Loewinson-Lessing supposes that the average rock may be about the mean of an average granite and an average basalt; Daly argues in favor of a fundamental basaltic magma; Mennell, whose experience has been gained in a granitic region, regards granite as the dominant rock with all else of minor importance. Mennell makes a strong argument in favor of his contention; but there is weighty evidence against it. If we study recent lavas, that is, the rocks which issue from unknown depths far below the surface, we shall see that rhyolite, the effusive equivalent of granite, is much rarer than andesite or basalt. The Deccan trap, the Columbia River basalt, the andesites of South America, the lavas of Iceland and the Hawaiian Islands are good illustrations of this statement. Moreover, the river waters which originate in areas of crystalline rocks contain almost invariably an excess of lime over soda, which would hardly be the case were granite predominant. Much socalled granite is really either quartz diorite or quartz monzonite, rocks which are probably far more abundant than has been commonly supposed.

In order to test the method of averaging analyses we may now compare the averages so far obtained by different computers, and then pass on to averages of rocks from distinct and widely separated areas. In these averages only the more important constitu