666 Dynamic Theory. 



ceeding from them are only reverberations of peripheral stimuli ; and 

 second, that since these phenomena are thus shown to be of the same 

 essential nature, and since one set, namely, those manifested through 

 the medulla oblongata and optic lobes alone, are purely automatic, it fol- 

 lows that the other set in which the cerebrum is also involved, are like- 

 wise purely automatic. ( This subject will be taken up again.) 



What we call the Will arises from action taking place in the cerebrum, 

 and is therefore to be classed as a function of the cerebrum. Its nature 

 is discussed in a separate chapter. In man and the monkey, destruction 

 of the motor areas of the cortex of the cerebrum produce complete paral- 

 ysis, and nothing can be added to this by the destruction of the corpus 

 striatum. In the case of the dog the destruction of the cortical motor 

 areas causes only partial paralysis, but if the corpus striatum and motor 

 part of internal capsule be also destroyed the paralysis is complete, ( at 

 least for a time,) and the dog lies entirely powerless and helpless. In 

 the case of the rabbit, destruction of neither the cortex nor the corpus 

 striatum nor of both are able to abolish the animal's power of balancing 

 or locomotion. 



These facts go to show that in Man and Monkey the cerebrum has 

 superseded the lower centers of sensation and motion to a larger extent 

 than in the Dog, Rabbit, &c. That is, the motor actions of man per- 

 formed now are stimulated by the sensoiy agitations, not only of to-day, 

 but by those of } 7 esterday, of last week, of last year, or even of last 

 centmy ; the sensory impressions of such agitations remaining in the 

 cerebrum in a condition to produce memories. In the dog the cerebrum 

 is relatively smaller, and so, fewer of his actions are due to former sen- 

 sations and more to present ones, the latter doing their work largely 

 through the lower centers, while the former do theirs chiefly, if not ex- 

 clusively, through the cerebrum. 



CHAPTER LXIY. 



MEMORY. 



It was pointed out in chapter 62 that the general cranio-spinal ner- 

 vous and ganglionic system divides into five separate subdivisions, each 

 of which may be operated in some degree of independence from the 

 others. The first of these is the Spinal Cord, the stimulation of which 

 from external sources, when not interfered with by the other ganglionic 

 centers, overflows at once to motor nerves and causes a muscle contrac- 

 tion. This sort of action is called Reflex. Next is the Medulla Ob- 

 longata. The motor action here arises from stimuli received from more 

 varied sources, and it affects not only external muscles, but glands, the 



