418 NATURAL SCIENCE [December 



assume all manner of different appearances by appropriate previ- 

 ous manipulation, so that the attitude can be of a most bizarre 

 kind. During the continuance of the immobile state the organs 

 of sensation, peripheral and central, show no evidence of any alter- 

 ation, and the animal thus appears to be conscious of the various 

 sensations produced by external impressions, but if these are suffi- 

 ciently intense to evoke an efferent discharge from the cerebral 

 hemispheres, the state at once ends and recovery takes place. This 

 recovery is shown to be ushered in by augmented contractions of those 

 muscular groups which are in the state of more pronounced contrac- 

 ture ; at first these are ineffectual to alter the position of the whole 

 body, but with their repetition the contracture subsides and the alter- 

 ation is effected. The author has not been able to confirm Danil- 

 ewsky's observation that during the state reflex excitability is lowered ; 

 he regards the previous evidence of such lowering as due to the 

 peculiar condition of the muscles, which owing to contracture are 

 incapable of adequate response to central nervous discharge. Lowered 

 reflex excitability only occurs when an animal has been manipulated 

 many times in rapid succession, in which case central fatigue mani- 

 fests itself and the contracture is correspondingly diminished. It will 

 be seen from the foregoing description that the characteristic condition 

 of the muscles, i.e. tonicity, disproves the existence of any inhibition 

 of lower neuro-muscular mechanisms during the state ; on the con- 

 trary, the lower centres — cerebellum, medulla, &c, being released from 

 cerebral control, now discharge a continuous stream of nervous im- 

 pulses such as occurs in the decerebrate mammal, and this produces 

 the marked decerebrate rigidity described by Sherrington, Horsley, 

 and others. 



With regard to the second factor in the production of the state, it 

 is shown* that the cessation of the discharge of impulses from the 

 cerebral cortex is a complete one. Such complete cessation must 

 exist when the cerebral hemispheres have been previously removed ; 

 in such animals the immobile state can be produced with great ease, 

 and is always of a most prolonged type, whilst the stimulating agencies 

 necessary to produce recovery, have to be of an intense character. In 

 the intact animal the author considers that the sudden cessation of 

 cerebral discharge cannot be explained as due to the lack of stimu- 

 lation of the motor areas existing in the cerebral cortex since the 

 physiological avenues for sensation are unaffected. He believes that 

 the paralysis of these centres is brought about by a sudden inhibition 

 due to the activity of special parts of the nervous system or to special 

 conditions of the centres themselves. His conception of such condi- 

 tions is set forth at some length in the concluding chapters of the 

 work, and is framed upon the lines of Hering's well-known views of 

 the physiological states of activity and repose. 



The whole work affords most striking instances of the opposite 

 roles to be assigned to cerebral and to lower centres respectively, 

 hence, its perusal may be confidently recommended to all those whose 

 special interests lie in physiology or neurology. But apart from the 

 obvious scientific value of the book, the earlier chapters contain a de- 

 scription of phenomena which will enable those interested in hypnotism 

 to realise what the so-called hypnotic state of an animal is like, and 



