It is a commonplace to talk of the machinery of the body, but it is not widely realised how close are the analogies which can be drawn between every detail of our physical structure and some feature or process of modern mechanical engineering. Professor Keith, realising how very much more most of us know of the working of an engine which comparatively few of us possess, an internal combustion engine, than of the working of the engines which we all possess in our muscles, has written a most informing and entertaining book, in which the mechanism and functions of our bones, muscles, heart, lungs, joints, brain, and other structures are considered in terms of their engineering analogies. It is hard to imagine a clearer or more charming exposition of elementary physiology. The book is based on a course of Christmas Lectures given at the Royal Institution, lectures primarily intended, as every one knows, for children. While there is little in the book which cannot be understood by any intelligent boy—that we do not add "or girl" is due to no reactionary denial of the full equality of the sexes, but to a belief that, at present, girls take less interest in, and so are less conversant with, the working of motor-car engines than boys—few grown-ups, even medical men, will read it without lively interest or without learning much. There is hardly any function or structure in our bodies for which Professor Keith does not find a counterpart in iron or steel—the internal texture of a bone is likened to Fairbairn's crane, a diagram of a force pump compared part by part with the diagram of the left ventricular pump of the heart. The varying length of heel found in different races is considered from the point of view of its mechanical usefulness in different circumstances, the superiority of the ape type of arm to the human type for the tasks which confront an ape is made clear in a few words. A short historical sketch of what Harvey was taught concerning the blood, contrasted with the wonderful new knowledge which he himself discovered, and the road by which he arrived at it, affords an admirable example of scientific method. These are citations at random; the whole book is full of commendable things. The bearings of recent research, such as the work of Haldane on Respiration, Cannon on Adrenalin, Starling on Hormones, are skilfully indicated in simple language. We congratulate Professor Keith on the production of a book of popular science which in clearness, depth of knowledge, and charm of style challenges comparison with the books which his great predecessor, Faraday, founded on his "Christmas Lectures."
PROBLEMS OF COSMOGONY AND STELLAR DYNAMICS. By J. H. Jeans. Cambridge University Press. 21s. net.
We welcome the appearance of this book, which is the essay to which the Adams Prize was adjudged in the year 1917. With the exception of Poincaré's well-known Leçons sur les Hypothéses Cosmogoniques there is, we think, no other book of recent date dealing authoritatively with the attractive subject of cosmogony, and in certain respects Mr. Jeans's book is a considerable advance on Poincaré's. The treatment is more systematic, and the author's own extensive contributions to the subject add to its value.
The introductory chapter gives a survey of the scientific problem of the origin of the universe, and points out the various uniformities which we have to explain. It also includes a brief historical sketch of the various theories of cosmogony put forward, from the famous nebular hypothesis of Kant and Laplace up to modern times. This chapter and the concluding chapter, on the Origin and Evolution of the Solar System, are accessible to the non-mathematical reader, and enable him to put himself in touch with the latest observations and speculations on these fascinating themes. The remainder of the book is highly mathematical, yet the author has presented his analysis so skilfully that a moderate knowledge of the calculus and dynamical principles suffice for the following of all the deductions. The general dynamics and criteria of stability and instability are first developed, and then the classical configurations of equilibrium of a rotating homogeneous mass—Maclaurin's spheroids and Jacobi's ellipsoids—are handled. Further systematic investigation leads up to the study of the oft-attacked, formidable problem of pear-shaped figures of equilibrium, which occupied the attention of Poincaré, G. Darwin, and Liapounoff. So far there has been question of stable configurations of equilibrium: the author now passes to the dynamical problems presented when there is no stable equilibrium, remarking that "a statical problem may or may not admit of solution, but a dynamical problem must always have a solution." Poincaré's "cataclysm" is for him merely a passage from a statical to a dynamical investigation. Soon, after summarising the results for a mass of fluid which is incompressible and homogeneous, he proceeds to consider the case when neither of these conditions pertain. Here we are presented chiefly with the important advances made by Mr. Jeans himself. The evolution of rotating nebulæ and of star clusters, of double and of multiple stars (particular attention being given to the process of fission and the subsequent motion), come up in turn for consideration, and from these gigantic voyages through space we return, at the end of the book, to our relatively minute solar system and its evolution. The book is illustrated with beautiful reproductions of photographs of nebulæ, taken at the Mount Wilson Observatory, and is in every way worthy of its author and its Press.
ARCHIVES OF RADIOLOGY AND ELECTROTHERAPY FOR DECEMBER. Heinemann.
The December number of the Archives of Radiology and Electrotherapy contains an interesting article on the work of the British Association of Radiology and Physiotherapy. One of the first fruits of its activities is that, at its instigation, the University of Cambridge has decided to institute a Diploma in Medical Radiology and Electrology. A knowledge of the properties of the various radiations of electrical origin on nature, of direct and alternating currents, and of electrotechnics in general, is of such importance in modern medicine that we heartily welcome the institution of a Diploma which will guarantee that its possessor has a thorough knowledge of the new and special technique required for the various electric treatments of to-day. The syllabus of subjects and the regulations governing the award, which provide, among other things, that the candidate must hold a recognised medical qualification, are published in full in the number of the Archives under notice. A study of the syllabus of the course of studies provided at Cambridge emphasises the range of physical phenomena, which have a therapeutic value—radiant heat, X-rays, the rays from radioactive substances, electrolysis, direct and high frequency currents, and static electricity, to name some of the most important. Obviously it is time for adequate provision to be made for instructing the medical man in the theory and manipulation of the machines and devices peculiar to this side of his art, since the average M.D. has not a very deep knowledge of physics. The only suggestion we would offer is that some attempt might be made to simplify or standardise the nomenclature of the subject. A glance at this short notice will show the variety of titles given to the new therapeutics, and of these the word "electrology," for instance, is given in Webster as "obsolete or rare." Surely there are sufficient terms already without reviving it.
BOOK-PRODUCTION NOTES
By J. H. MASON