354 APPENDIX. 



muscles of respiration. The lumbar plexus, k, which 

 supplies the back, or lumbar region, passes to the ante- 

 rior regions, and supplies the front of the legs. The 

 popliteal plexus, /, is a continuation of the sacral plexus, 

 and supplies the ham and parts adjoining. 



Functions of the Brain and Spinal Cord. The cere- 

 bral system of nerves conveys the impressions from ev- 

 ery part of the body to the brain, where they are com- 

 municated to the mind, that is, the individual becomes 

 conscious of them, or feels them as sensations. And 

 by the fibres of the same system, which pass from the 

 brain to the muscles, the will acts upon these in produ- 

 cing voluntary motion. Now the brain is not in constant 

 action, even in a healthy state, for it requires rest ; and 

 during profound sleep, it appears to be in a state of com- 

 plete torpor. Yet the motions of the voluntary muscles 

 may still act, for if a liquid be poured into the mouth, it 

 is swallowed, and the position of the body is changed, 

 as it becomes tired of one position. In apoplexy, also, 

 when all the senses are suspended, irritation produces 

 action, for if the nose be tickled, the hand is raised to 

 remove the offending cause. Similar phenomena take 

 place in animals, where the cerebrum has been removed, 

 or where the functions are completely suspended "by a 

 blow on the head. If, in such cases, the eyelid be touch- 

 ed with a straw, the lid instantly closes. If the lid be 

 open, and a candle be brought near the eye, in the night, 

 the pupil contracts ; and if the foot or hand be pinched 

 or pricked, it is instantly removed. 



Dr. Carpenter states that in one of the experiments 

 made with the view of ascertaining the degree, in which 

 the activity of the cerebrum is essential to the maintain- 

 ance of life, a pigeon was kept alive (if alive it could be 

 called) for some months after the removal of its cere- 

 brum, running when it was pushed, flying when it was 

 thrown into the air, drinking when its beak was plunged 

 into water, and swallowing when food was put into its 

 mouth ; but at all other times, or when left to itself, it 

 appeared like an animal in a profound slumber. Of the 

 humanity of such experiments it is needless to speak, 



