Conditioned Reflexes. An Investigation of the Physiological Activity of the Cerebral Cortex: By I. P. Pavlov. For. Mem. R.S. Translated and edited by G. V. Anrep, M.D., D.Sc. (Oxford University Press, Humphrey Milford, 1927. Pp. 430. Price 28 s.)

This is one of the most important and original books ever published on the nervous system. The main outlines of Professor Pavlov's researches have been known for some years, but here we have for the first time a complete presentation of them in English. The work of translating and collating them must have been very great indeed, and it has been excellently performed by one of his own colleagues who is now a lecturer in the University of Cambridge.

Professor Pavlov sets himself the task, among others, of describing animal pathology in physiological terms. He deliberately excludes psychological considerations, and the following passages give a plain hint of his grounds. 'In fact it is still open to discussion whether psychology is a natural science, or whether it can be regarded as a science at all'. 'Such testimony seems to show clearly that psychology cannot yet claim the status of an exact science' (p. 3).

In an interesting chapter where the applications to man are discussed, the author considers problems of mental disorder. He is evidently very much at sea in this field, but none the less there are some interesting correlations between his work and that of psychopathologists. For instance, his main point of view is the contrast, or conflict, between the processes of excitation and inhibition of response, and he attempts to group nervous reactions on this basis. 'So far as can be judged on the basis of casual observation I believe that these two variations in the pathological disturbance of the cortical activity in animals are comparable to the two forms of neurosis in man—in the pre-Freudian terminology neurasthenia and hysteria —the first with exaggeration of the excitatory and weakness of the inhibitory process, the second with a predominance of the inhibitory and weakness of the excitatory process' (pp. 397, 398).

The time is not yet ripe for this important correlation between psychology and physiology to be profitably attempted, but when the time comes Pr