145 



advances with increasing precision. The general assignment of 

 digestion to the stomach, of circulation to the heart, and of 

 breathing to the lungs, has become very specific; and far 

 minuter knowledge may be regarded as certain. But there is 

 much less completeness when we come to ascribe to the brain 

 the functions and phenomena of thought. 



19. An organ truly ascertained to be such, shows its relation 

 to its functions by its fitness. Thus the orifices and valves 

 of the heart are clearly adapted to its office in Especially aa 

 the system. This kind of fitness, however, is net 'to the human 

 ascertained in the least, and it is difficult, as Dr. ^^^*°'^*' 

 Tyndall allows, to conceive that it ever can be, in respect of the 

 brain (p. 121). Though we do not, as in BuflPon's time, regard 

 the brain as mucous substance of an unimportant character, 

 yet there is nothing apparently in its structure to suggest the 

 process of thought, as we have seen the contents of the cranium 

 lying before us in a basin, — nor even to vindicate altogether the 

 Cartesian notion that the pineal gland is the seat of the soul. 

 Let us ask how far physiology has proceeded in its analysis, 

 and we then may discover how much remains unapproached. 



It would seem fairly certain, for instance, that the cerebral 

 organization is enlarged in proportion as intelligence is manifest 

 in animals. In accordance, too, with the form of brain, and the 

 folds spread over its surface, there probably are different degrees 

 of inteUigence. There may also appear to be increasing com- 

 plexity of organization in the higher animal varieties. 



20. We may readily accept all this, and much more, on the 

 testimony of the scientific physiologist, until we have further 

 light. The conditions of life are, no doubt, phy- 

 Biologically similar in the cerebral and other organs. P^^'jjj'J^^y °^ 

 The blood conveys nutrition, warmth, moisture. 



Let the blood diminish its flow, and the activity of the organ 

 is at once affected. On a total withdrawal of blood we should ~ 

 expect that the brain would cease to act. A modification even 

 of the temperature of the blood has sensible effect on the brain. 

 (Some of us are certainly more equal to intellectual exertion 

 when we are, as we express it at times, " warm through.^^) 



In addition, too, to the law of general circulation, there is 

 some local law of action and repose, in the exam.ination of which, 

 however, we seem stopped. It is in this local department we 

 find the action of the nerves. While the muscular system acts 

 mechanically, the nervous system and the glands, which act 

 chemically, we are told, are subject to this local law. The brain 

 is no exception to the general law of the circulation of the blood, 

 nor to its local adaptations. In all this, however, we have 

 arrived at no analysis whatever of the thinker, or the thought; 



