November 12, 1891] 



NATURE 



27 



between the arteries and capillaries on the one hand, and 

 the veins on the other, as the key-stone of the theory of 

 the causation of sleep. The altered balance of the cir- 

 culation occasions a change in the balance of active 

 pressure, which is not so much within the brain substance 

 as on the surface. It is less expansive and more com- 

 pressing, and with this compression consciousness is 

 suspended. 



In proof of his theory, the author adduces observa- 

 tions made by Dr. Hughlings Jackson and himself on 

 the retina — the blood-vessels of which are so intimately 

 connected with those of the brain — both during sleep and 

 in a state of coma, from which it would appear that in 

 these conditions the retina was paler, its arteries smaller, 

 but its veins were larger, more tortuous, and distended. 

 In another case recorded by Dr. Kennedy, where a por- 

 tion of the skull and dura mater had been removed, and 

 the pia mater consequently exposed, it was noticed that 

 the veins in the latter were during sleep congested and 

 assumed a dark hue. 



In a concluding chapter, entitled " Some Points in 

 Mental Physiology," which was not contained in his 

 previous work " On the Immediate Cause of Sleep," the 

 author considers how far the pecuHarities of the en- 

 cephalic circulation may affect the functional activity of 

 the different parts of the brain. Starting from the position 

 that the brain is a composite organ, and that distinct 

 portions are put into a state of functional activity in con- 

 nection with the discharge of their respective duties, the 

 question of balance of the circulation has again to be 

 considered. For the part which is more immediately 

 concerned in the production of the particular cerebral 

 operation must become the seat of vascular excitement, 

 and the amount of blood flowing through its vessels will 

 be greater than that transmitted through the vessels of 

 those other parts of the brain which are for the time 

 being not so functionally active. Hence a certain tension 

 of the area or centre which is actively working must 

 arise, and the encephalic circulation is focussed in the 

 direction of activity. The parts which surround the 

 operating centre would act as a background of resist- 

 ance, and would afford such support as will secure the 

 immediate liberating action in the discharging centre. 



The author applies his views on the encephalic circula- 

 tion to the explanation of the phenomena of Hypnotism. 

 The first incident in the hypnotic state is a steady pro- 

 longed effort of volition in which the attention is con- 

 centrated in a very restricted direction. The immediate 

 consequence is fatigue of the nerve-centres concerned in 

 keeping up the strain. Their molecular motions become 

 enfeebled, the circulation through them is less active, 

 and a condition approaching that of sleep is produced. 

 If then, in the form of a "suggestion" from another, 

 some stimulus calls into activity a part of the brain not 

 fatigued in the effort of attention, the vascular activity in 

 it will be increased, and its function will be intensified. 

 An assertion boldly made to a hypnotized person may 

 influence belief in opposition to former experience, and if 

 it be towards an ideational centre, some particular notion 

 may so monopolize the consciousness that discrimination 

 and judgment may become almost as completely in 

 abeyance as in ordinary dreaming. 

 NO. I I 50, VOL. 45] 



OUR BOOK SHELF. 



Physiography: Elementary Stage. By J. Spencer, 



B.Sc, F.C.S, (London : Percival and Co., 1891.") 

 As an introductory science, physiography is one requir- 

 ing very careful treatment. Its range is undoubtedly 

 wide, but it is correspondingly shallow, and should rather 

 lead up to scientific thought than aim at giving an in- 

 coherent collection of facts. In the book before us, the 

 author, who is head master of one of our most successful 

 technical colleges, begins well by recommending that 

 teachers should endeavour to make the subject a prac- 

 tical one, by the performance of experiments, excursions 

 into the neighbouring country, and the collection of 

 specimens of rocks, minerals, and fossils. The experi- 

 mental shape which the book has consequently taken is 

 one of its most noticeable features ; but it certainly falls 

 short of the expectations raised. The chemical and phy- 

 sical parts appear to be excellent, but there is little to 

 assist either teacher or student in gleaning information 

 from the inspection of natural phenomena. A peat bog, 

 for instance, is a fruitful subject for study under proper 

 guidance ; but this is not afforded by the scanty remarks 

 on p. 89, In dealing with a wide subject, brevity is 

 essential, but this does not necessitate the omission of 

 the fundamental points, and looseness of expression. 

 The book, however, shows many signs of a want of care 

 in this respect. In the note on Foucault's pendulum 

 (p. 210), for example, the whole point of the explanation 

 is lost Isy the absence of a reference to the permanence 

 of the plane of swing. On p. 113, it is stated that " sub- 

 marine volcanoes produce new land, the erupted matter 

 being piled up sufficiently high to form islands " ; the 

 omission of the qualifying word " sometimes " might 

 obviously lead to a misconception. Test questions, ori- 

 ginal and selected, are given at the end of each chapter. 



The book is well illustrated, and, with careful revision, 

 should make a useful addition to existing text-books. 



Mayhew's Illustrated Horse Doctor. Revised ana Im- 

 proved by James Irvine Lupton,'F.R,C.V.S. (London : 

 Griffith, Farran, and Co.)' 



The contmued existence of domestic meaicine, whether 

 the subjects of its application be human beings or 

 domesticated animals, cannot well be doubted. We may, 

 however, be permitted to doubt whether true economy 

 lies in this direction. Nevertheless, as residents in the 

 colonies, and even in many rural districts of our own 

 country, are often far removed from the qualified veteri- 

 narian, and considerable time must necessarily elapse 

 before his services when sought can be forthcoming, it is 

 obviously advisable that whatever measures are taken by 

 the stock-owner to ameliorate the sufferings of the animal 

 during this interval of time should be rational, and follow 

 lines similar to those which the professional man would 

 adopt. Wrong methods of procedure would serve only 

 to handicap and hamper his efforts. The book before us 

 can be recommended to guide the horse-owner in such 

 emergencies ; though we note with pleasure that the re- 

 viser, on p. 553, points out that "the reader will always 

 best consult his interest and pocket by at once consulting 

 a qualified veterinarian." Agreeing with this proposition, 

 we cannot but consider superfluous the introduction of 

 minute directions for the performance of such delicate 

 and difficult operations as the extirpation of the eye-ball, 

 the division of the plantar nerves (neurotomy) in some 

 forms of foot-lameness, and section of contracted tendons 

 (tenotomy). We can scarcely conceive an owner, how- 

 ever intelligent and courageous he may be, proceeding to 

 cast, chloroform, and perform any of the above-mentioned 

 operations. 



Horse-owners will do well to note the stress which is 

 laid upon the construction, ventilation, and drainage] of 



