NECESSITY OF REST AND RECREATION. 259 



rest, quiet, and recreation. 4 The mind ought sometimes to 

 be amused, that it may the better return to thought and to 

 itself.' 1 ' Unzer explains that by deep and intense thought 

 the body wastes, the blood is determined to the head, the 

 extremities become cold, the blood is altered in composi- 

 tion, and a paraesthetic condition of the nervous system 

 results, while the viscera perform their functions imper- 

 fectly.' ' Hence it follows that deep studies and scientific 

 pursuits are not the most natural objects of man, but 

 opposed to his health and well-being. Thus it is that those 

 learned men who cultivate the abstract sciences are 

 generally feeble, meagre, sensitive, splenetic, hypocon- 

 clriacal, and fanciful, and have impaired digestion. On the 

 contrary, the strongest and healthiest men, with good 

 digestion, are little given to study the abstract sciences 

 and little capable of comprehending them.' 2 c Boerhaave 

 is recorded not to have closed his eyes in sleep for a period 

 of six weeks, in consequence of his brain being over- 

 wrought . by intense thought on a profound subject of 

 study.' 3 



That the ability to secure a sufficiency of sleep is indis- 

 pensable to long-continued pursuit of recondite scientific 

 researches is very manifest, for no man can prosecute diffi- 

 cult intellectual labour without intervals of mental rest. 

 The phenomena which occur in complicated structures, 

 especially in living bodies, are nearly always dependent 

 upon a plurality of conditions. In accordance with this 

 general truth sleep is an effect difficult to produce, because 

 it depends upon so many conditions, the actions of most 

 of which are at present very imperfectly understood ; and 



1 Phaadrus. 



2 W. C. Mclntosh 'On Morbid Impulse,' Psychological Journal, 

 1863, p. 119. 



3 F. Winslo Obscure Diseases of the Brain and Mind, p. 604. 



S 2 



