On the Scientific Study of Human Nature. 465 



the faculty of speech may be partially or wholly destroyed, 

 the memory of words confused, or entire parts of speech 

 lost. 



Mental perversions are also caused by certain changes 

 in the properties of the blood. A fluid of amazing com- 

 plexity, holding in exquisite balance the constituents from 

 which the whole being is elaborated, all delicacies of feel- 

 ing and niceties of thought depend upon its purity. " Pol- 

 ished steel is not quicker dimmed by the slightest breath 

 than is the brain affected by some abnormal conditions of 

 the blood." 



If the poisonous products of bodily waste are not con- 

 stantly swept from the system, the cerebral changes are 

 disturbed and the mind stupefied. Foods, drinks, and 

 drugs affect specifically the appetites, passions, and 

 thoughts. To become exhilarated and joyous, man 

 charges his blood with wine; to exalt the sensations, he 

 takes hashish ; to secure a brilliant fancy and luxurious 

 imagination, he uses opium ; to abolish consciousness of 

 pain, he breathes vapour of chloroform. Swedenborg had 

 a peculiar class of visions "after coffee." "A person I 

 know," observes Dr. Laycock, " after taking morphine, in 

 a fever, was haunted by hideously grotesque and fiendlike 

 spectres ; they then shortly changed into groups of comical 

 human faces, and finally altered to forms of the human fig- 

 ure of the most classic beauty, and then disappeared." And 

 this learned inquirer maintains that the pictorial productions 

 of the insane vary in a definite order, the early stages of 

 excitement enabling the artist to execute beautiful concep- 

 tions of figures and landscapes; then, as the disease ad- 

 vances, he passes into comic delineations, and ends with 

 the grotesque, or hideous. 



Those fluctuations of feeling with which all are more or 

 less familiar, the alternations of hope and despondency, 

 are vitally connected with organic states. In high health, 



