126 SCIENCE PROGRESS 



developed in response to local conditions. It is concluded that 

 this astonishingly large number of endemics owes its origin to 

 mutations which may be almost of generic amplitude — the 

 endemic species do not show close similarity to their nearest 

 relatives. 



PHYSIOLOGY. By W. L. Symks, M.R.C.S., University of London. 

 The most interesting event of recent months is the issue of a 

 volume of Abstracts of papers in physiology and related sub- 

 jects by the Physiological Society of Great Britain and Ireland, 

 with the co-operation of the American Physiological Society 

 and of other societies and journals in this country and abroad. 

 The publication should be seen by all whose work and interests 

 are touched by physiology. It is reviewed in a later page (176) 

 of this number. 



The Journal of Physiology (vol. 1.) presents a new feature, 

 viz. a paper on history, in which Langley describes the progress 

 of discovery, as regards the autonomic nervous system, during 

 the eighteenth century. Of particular interest and value would 

 be an extension of that history to the present time. So much 

 of it arose in Cambridge that its collation, and presentation, 

 by Cambridge would be peculiarly appropriate. 



Two papers on muscle tonus appear in the current (vol. 

 xxxviii.) issue of Brain. In the first of these Sherrington defines 

 tonus as a posture, and contrasts the conditions during tonus 

 with those during actual shortening of muscle. In the second 

 paper Langelaan defining tonus in terms of the change pro- 

 duced by increasing the muscular load, discusses the role of 

 " elasticity " and of " plasticity " in this state. His definition 

 of elasticity is unfortunate, and must be kept clearly in mind 

 if the paper is to be understood . Van Rijnberk (Arch. Ne'erland, 

 vol. iii. B) also contributes an interesting paper on muscle tonus. 

 He has investigated the paradoxical lingual phenomenon of 

 Vulpian, together with the pseudo-motor reaction (Rogowics) 

 of the dog's lip, and concludes that these represent varying 

 tonus of striped muscle and not merely vaso-motor changes. 

 All these papers dilate on the dual contractility of muscle 

 already described, or implied, by previous writers (notably by 

 Botazzi, by Boeke, by de Boer, and by Graham Brown), in 

 connection with the dual efferent innervation by cerebro-spinal 

 and by autonomic nerves respectively, 



