THE HYPOTHALAMUS

This splendid monograph is based upon four lectures, now elaborated and brought up to date, which were delivered in 1936 under the auspices of the William Ramsay Henderson Trust. EaXch of the lecturers in his own sphere has long made a special study of the anatomical, physiological, clinical, or surgical problems presented by the hypothalamus-that tiny fraction (less thai 1 /250th) of the brain which is now known to exercise so profound an influence over the most fundamental of our bodily and psychic activities. There is surprisingly little overlapping in the lectures as now published, and when repetition has been unavoidable the different angle of approach merely corroborates some earlier observation and helps the reader to fix important facts in his memory without the tedium inevitably produced by simple reiteration. Furthermore, no attempt has been made to write a big book; the literary style is admirable throughout, for without wasting words the information gleaned from personal experience has been clearly set forth, and the involved problems have been referred to with the modesty and wisdom which characterize only those who appreciate the limitations of their knowledge. Professor Le Gros Clark deals with the histological structure of the mammalian hypothalamus, and discusses the comparative anatomy of these parts in the lower vertebrates, finally contrasting the features in the lower forms with those found in the human brain. An extremely interesting section of this lecture deals with the rich blood supply to the hypothalamus, and the theory that the hypophysis nlay be functionally linked to the hypothalamus by a hypophyseo-portal system of blood vessels is thoroughly considered, though it seems to be impossible at present to arrive at a definite conclusion on this matter. The functional aspects of the hypothalamus are reviewed by Dr. John Beattie, who puts forward his reasons for regarding the hypothalamus as having a dual mechanism, one part activating the parasympathetic and the other the sympathetic portion of the autonomic system, the two parts being antagonistic yet controlled so as to maintain a constant internal environment within the body. As he justly remarks, if the complicated structure of the hypothalamus, with its numerous centres and tracts, does not seem to harmonize with such an apparently simple dual mechanism, then the only alternative is to regard the hypothalamus as a single unit, comparable to the cerebral cortex in its method of receiving, selecting, and transmitting nerve impulses to and from other parts of the nervous system. It is difficult to decide which of these two conceptions approximates more closely to the truth, but the theory of the dual mechanism offers a satisfactory explanation for the reactions of the body to cold and heat. Dr. Beattie also discuSses the relationship of the hyp'ophysis to the hypothalamus. A nervous pathway connecting the two is readily demonstrable ; the possibility that chemical substances may pass from the hypophysis more or less directly to the hypothalamus cannot be denied; but the balance of evidence at the moment seems to be against a direct connexion by a system of " portal " blood vessels. The lectures by Dr. George Riddoch and Mr. Norman Dott on the clinical and the surgical aspects of hypothalamic disorders are full of interest, not only to the neurologist but to the general physician as well. Every thoughtful surgeon must also find that these clinical records throw fresh light upon many of the yet unsolved problems of visceral disease, such as gastric ulceration, the sequelae of cerebral injury, and certain metabolic upsets. In addition to a masterly description of the clinical manifestations of derangements of the hypothalamus, Dr. Riddoch gives us a very clear account of an astonishingly large number of pathological processes which may be responsible. Mr. Dott's contribution is a remarkable testimony to the value of surgery as an instrument of research, and a brilliant exposition of how much may be gained from the painstaking study of a comparatively small group of patients. The monograph is beautifully illustrated, Mr. Chesterman's photomicrographs and Miss Thom's drawings being particularly praiseworthy; and a full bibliography puts the finishing touch to a classical contribution to medical literature.