INFLUENCE OF INTENSE STUDY. 957 



performance of which, the vital properties of the 

 blood, and the healthy activity of all the functions 

 depend. For it is certain that the life of the 

 brain, spinal marrow, ganglionic nerves, and 

 every part of the body, is derived from the blood, 

 which derives it from the atmosphere, while 

 passing through the lungs. It is therefore mani- 

 festly an error to maintain that the brain or 

 any other portion of the nervous system is the 

 source of vitality ; or that they exert any other 

 influence on the vital functions, except through 

 the medium of the lungs. 



Nearly the same effects are produced on the 

 constitution of man by intense and long continued 

 study, as by the depressing emotions ; especially 

 when the subject of inquiry involves at every 

 step, principles of the widest span, and therefore 

 keeps the intellectual faculties on a perpetual 

 strain.* Hence it is rare to find the highest de- 



* The pathological history of literary and scientific men af- 

 fords innumerable examples of the dangerous consequences arising 

 from over-exertion of the intellectual faculties. No enlightened 

 medical man can read the life and correspondence of Sir I. New- 

 ton, without being convinced, that for the space of two years, he 

 laboured under a state of partial insanity, brought on by his 

 excessive devotion to mathematical and physical researches, 

 aided, perhaps, by anxiety in regard to the extreme narrowness 

 of his income. Had not his labours been rewarded by a lucrative 

 office under government, and crowned with glorious fame, it is 

 probable that he would have sunk into a state of permanent 

 melancholy, if not madness; and have died prematurely of apo- 

 plexy or paralysis, which carried off Sir Walter Scott in the sixty- 



