NERVOUS SYSTEM. 161 



are more or less intimately related. This connection is 

 very conspicuously displayed in those actions which arise 

 from what is termed sympathy. Thus, an injury on the 

 toe will sometimes bring on lock-jaw ; certain smells will 

 occasion sickness ; terror will cause the heart to palpitate, 

 the cheek to turn pale, and augment the secretions of the 

 intestines and bladder. The sight of a good meal to a 

 hungry man makes his mouth water. 



This intimate connection between the different parts of 

 the nervous system, is likewise very strikingly displayetl 

 in the case of poisons. Many kinds of poisonous substan- 

 ces, when applied to the stomach, speedily bring on death, 

 by annihilating the energies of the nerves of that organ, 

 and indirectly the vitality of the whole nervous system. 

 The removal of the brain is likewise followed by the loss 

 of power in the nerves. 



But this intimate connection, between the different parts 

 of the nervous system, becomes scarcely perceptible in the 

 lower orders of animals. Where the bulk of the brain is 

 greatest in proportion to the nerves connected with it, as in 

 man, we find this union most intimate. As the bulk of the 

 brain decreases in proportion to the bulk of the nerves, the 

 connection ceases to be so close. In reptiles and fishes, this 

 is so conspicuously displayed, that it becomes difficult to in- 

 duce death. The brain, or the spinal marrow, may be re- 

 moved, and yet the other functions of life still proceed for 

 a considerable time. Among the mollusca, an equal want 

 of sympathy among the different parts, is well known to 

 prevail. As we descend still lower, to those animals in 

 which the nervous system, instead of appearing in the form 

 of brain, nerves or ganglia, is uniformly diffused, we ob- 

 serve scarcely any dependent connection between the dif- 

 ferent parts. When portions of the body are removed, 

 vor. i. i. 



