8o4 THE POPULAR SCIENCE MONTHLY. 



any, in jn'oducing the effect. That it is not an essential factor is, to 

 some extent, confirmed by the fact that a frog without the cerebral 

 hemispheres can be easily mesmerized ; it is difficult to conceive of the 

 animal in this state being very much frightened. 



It will be remembered that reflex action from all parts of the body 

 is diminished in the mesmerized frog. After a time, then, there is a 

 marked inhibition of activity of the whole nervous system. Now, in 

 the brainless frog placed on its back there is no such diminution of 

 reflex action ; hence in the intact hypnotized frog the spinal cord must 

 be inhibited by impulses coming from the brain ; from which we may 

 conclude that centers inhibited in their own proper action nevertheless 

 send out inhibitory impulses to other centers. There appears, then, to 

 be an irradiation of inhibitory impulses, just as we have seen that 

 there is an irradiation of exciting impulses. 



Before passing to mesmerism in man I will show you two other 

 instances of hypnotism in the lower animals. The alligator which you 

 see here behaves very much like the frog. It has, however, less tend- 

 ency to become cataleptic. After a brief struggle, it becomes quies- 

 cent and its limbs slowly relax ; its mouth may then be opened, and 

 a cork placed between its teeth, without giving rise to any voluntary 

 movement on its part. It may be kept for a considerable time in this 

 limp condition by gently stroking the skin close to its eyes. 



So far as I have observed, the hypnotic condition in birds and in 

 lower mammals is not capable of any great development. It may last 

 ten minutes, but rarely longer. In these animals, too, the emotional 

 condition is probably the chief factor in producing the inhibition. Of 

 impulses from peripheral sense-organs, tactile impulses seem to be most 

 effective in the lower mammals, as in the rabbit and Guinea-pig, and 

 visual impulses in the bird. The pigeon which I have here remains 

 longest quiescent when, after it has been held for a minute or two, I 

 bring my hand slowly up and down over its head. 



In man the phenomena of mesmerism are of a very much more 

 striking character than they are in the lower animals. Speaking gen- 

 erally, this seems to be due to a greater interdependence of the various 

 parts of the nervous system in the lower animals. In these, when any 

 one center is stirred up by exciting impulses, an irradiation of exciting 

 impulses is apt to take place to all other centers, and the mesmeric 

 state is in consequence apt to be broken. And on the other hand, 

 when a center is inhibited, an irradiation of inhibitory impulses is apt 

 to take place, and the whole nervous system is in consequence apt to 

 be inhibited. Hence the activity or suppression of activity of particu- 

 lar parts of the central nervous system, which forms so conspicuous a 

 feature of mesmerism in man, can be only partially produced in the 

 lower vertebrates. Even in man there is very considerable difference, 

 in different individuals, in the ease with which particular nerve-centers 

 can be excited or inhibited without other centers being similarly af- 



