62 GENERAL ANALYSIS. 



149. To PRODUCE A SENSATION, there is necessary a 

 portion of Brain, called a Sensatory Ganglion, active to 

 such a degree and in such a way as to excite in the mind 

 a sensation. 



150. THE SENSATORY GANGLIA ARE CONNECTED only 

 with the Mind, with other parts of the Brain, and with 

 the Sensatory Nerves, which are in one sense the white 

 part of the Ganglia, or continuations of it, reaching or 

 extending out, in the form of minute pulpy cords, into all 

 parts of the body, and almost to its very surface. (PI. 3.) 



151. THE ACTIVITY OF A SENSATORY GANGLION, and 

 consequently a sensation, must be caused either, 



1st. By the action of the Mind upon the Ganglion, 

 causing reaction upon itself; which is doubtful. 



2d. By the action of other parts of the Brain. 



3d. By the action of the Ganglion itself. This may 

 easily be the case, for blood is constantly circulating 

 through it, and changes are thus constantly taking place 

 in the ganglion, and it must be constantly active, if not 

 to the degree to cause sensation. 



4th. By the action of the sematory Nerves. 



152. THE immediate CAUSE OF SENSATION is always 

 a Ganglion, but that which excites the ganglion to sensa- 

 tory activity, no matter through what steps, is commonly 

 called the cause of the sensation and of the activity of 

 the Ganglion ; therefore it is caused, 



5th. By the action of the general organs, in which 

 the outer extremities of the general sensatory nerves 

 are found ; the organ exciting the nerve, and the nerve 

 exciting the ganglion ; thus by two steps its activity is 

 excited. 



6th. By the action of the special organs in which 

 the special sensatory nerves commence outwardly. In 

 this case through two steps the ganglion is excited. 



7th. By the action of external objects, through the 



149. What is necessary ? 150. How ? 151. How must 1st ? 2d ? 3d ? 4th ? 

 152. What is ? How is sensation caused ? 5th ? 6th ? 7th ? 



