1884.] on the Physiological Aspect of Mesmerism. 27 



Primarily, the hypnotic or mesmeric state is one in which the 

 will is partially or wholly paralysed by certain sensory impressions ; 

 but there is no distinct line of demarcation between this and 

 various other conditions, such as occur in sleep, somnambulism, 

 and in some diseases of the central nervous system, such as hysteria. 

 In each there is a typical state, but between them are many transition 

 states. 



Before discussing the mesmeric condition, I must say one or two 

 words about the action of the central nervous system. I trust you 

 will forgive me if, as very well may be the case, you find that part of 

 what I say seems too simple to need saying, and part too complex and 

 uncertain to be said without reservation. The one for the sake of 

 clearness must needs be stated ; the other for the sake of brevity must 

 needs be dogmatic. 



Here is a diagram of the brain and of the spinal cord of the frog. 

 In this, all the chief structures of the brain of man are represented. 

 For my present purpose it is only necessary to distinguish three 

 divisions. 



First there is the spinal cord. If a frog be decapitated, the brain 

 is of course removed and the spinal cord is the only part of the central 

 nervous system left. Yet if any part of the body of the brainless frog 

 be gently stimulated, a particular movement results — a reflex action is 

 produced. If, for instance, the right hind leg is gently pinched, this 

 leg and this only is kicked out ; if the left fore leg is gently pinched, 

 this and this only is moved. Diagrammatically we may represent any 

 one of these movements as being brought about in the following way. 

 Pinching the skin stimulates the nerve endings of a sensory nerve, 

 £0 that a nerve impulse — analogous to, but not identical with, an 

 electric current passing along a wire — travels up the nerve to a 

 sensory nerve cell in the spinal cord. In this nerve cell certain 

 changes take place which result in an impulse being sent along 

 another nerve to a motor nerve cell in the spinal cord. This is, in 

 consequence, stimulated to activity and sends out a third impulse along 

 a motor nerve to a muscle. The muscle then contracts, and the limb 

 is moved. 



If the brainless frog be pinched somewhat sharply, the movements 

 which result are more extensive than when it is gently pinched, a 

 spasm of the whole body may result. Referring to the diagram, we 

 may represent this in the following way. The sensory cell being 

 more strongly aifected, sends out impulses to a number of other 

 sensory cells on the opposite side of the spinal cord, and above and 

 below it ; these send impulses to their motor centres, and thus a more 

 or less widely-spread movement results. This spreading out of im- 

 pulses from the part immediately affected is called the irradiation of 

 exciting impulses. When any part of the skin is stimulated, many 

 sensory and many motor cells are affected ; a collection of cells 

 serving a common purpose is called a nerve centre. The spinal 

 cord, then, consists of a collection of nerve centres. By appropriate 



