THE SPINAL CORD AND CEREBELLUM 125 



reflex by which it is brought about does not depend 

 on the perfect functioning of the peripheral sense- 

 organ is strikingly proved in the case of Beethoven; 

 for his symphonies, which constitute in the whole 

 realm of human production one of the most prominent 

 examples of intense cerebral action, were composed 

 after he had become a sufferer from deafness. This 

 shows that the main factor in the increase of sensation, 

 taken in its widest meaning, is an internal one, and 

 enables us to disregard to a great extent external 

 influences. 

 As it is, therefore, evident that all intensification of The phy- 



siological 



sensation is due in the main to an internal cause, it is mechan- 

 ism of will, 

 necessary to inquire further into the nature of it. It 



is a common thing to say of a person who has solved 

 some very difficult problem, he has worked it out by 

 an effort of ' will.' This means, if it have any physio- 

 mode of vibration of the ordinary sensory cells in which vaso- 

 motor activity plays a very important part. Thus, a condition 

 of relaxation or of too great expansion of the tissues, including 

 the nerve-oeUs, is a fertile cause of melancholy, and can often 

 be at once removed by the use of such a drug as strychnine, 

 which stimulates contraction. We see the fruits of this relaxa- 

 tion and melancholy in the increase in the number of suicides 

 which invariably takes place when the summer heat becomes 

 very oppressive. The actual cause of the melancholy and relaxa- 

 tion is probably to be attributed to a weakening of the heart's 

 action and a general diminution of blood-pressure and hence of " 

 oxidation. A sudden change from cold or cool to very hot 

 weather seems to affect the nerve-centres in an especial manner. 

 Irritability and excitabiUty may also be traced in a great 

 measure to causes connected with the vascular system and the 

 manner in which the processes of oxidation are carried out. 



