Some Accoun( of M.l^ichat'k Theory of Life. 171 



without any regard to the median line, and one half of it bears 

 no resemblance to the other; the same is true of the liver, the 

 spleen, and all the organic viscera. The heart, it is true, is a 

 double organ ; but its parts are of unequal size and strength ; 

 the rest ot the circulating system presents a thousand irregu- 

 larities ; and the lungs are dissimilar in the tvro sides of the 

 thorax, hi the division of their lobes, and the quantity of mat- 

 ter they contain. 



This symmetry of the form is accompanied by a corre- 

 sponding harmony in the functions of the organs of the animal 

 life. The exactness and perfection of vision depend upon the 

 similarity of the impressions transmitted by the two eyes to 

 the brain ; if these impressions are dissimilar, vision will be 

 imperfect in proportion ; hence we shut one eye when the 

 power of the other is increased by the interposition of a lens, and 

 hence we squint when one eye is made weaker than the other. 

 The same is true of all the senses, of the muscles of locomo- 

 tion and voice, and of the brain itself; if there is between the 

 corresponding oi'gans on the two sides, or tlie corresponding 

 halves of the organs, any inequality or dissimilarity, that is, if 

 there is any defect of symmetr}^, the consequence is an imper- 

 fection in their function. Upon this principle Bichat explains 

 the difference between different individuals in their natural 

 capacity for distinguishing accurately the harmony of sounds. 

 A good ear for music, as we express ourselves in common lan- 

 guage, is only the result of the possession of two symmetrical 

 organs of hearing, which transmit to the brain similar impres- 

 sions ; a bad ear, on the contrary, is produced by any in- 

 equality in the organs, which transmit two unequal impressions. 

 Thus, when one, either of our ears or eyes, is deprived of its 

 usual degi'ee of sensibility, we can hear or see much better by 

 making use of that alone, which is uninjured, than by having 

 recourse to both. The same remark is extended to the func- 

 tions of smelHng, tasting, and touching, and to the functions 

 of the brain and muscles. But nothing like this is true of the 

 organic life, to the regularity of whose ojierations, harmony 

 and correspondence ot action is not a necessary condition. 



The functions of the organic life are constantly going on ; 

 they admit of no interruption, no repose; whatever cause sus- 

 j)en(ls, but for a moment, the rcsj>ii'ation or the circulation, 

 destroys life. They form a necessary and coimected series, 

 which nnist l>e always moving on in continued }iiogression, 

 from the beginning to the end of existence. But in those of 

 the animal lite the case is widely diflerent. Tlicy have intervals 

 of entire repose. The organs of this life are incajjable of con- 

 slant activity, they become fatigued by exercise and re(]uirc 



Y 2 icst. 



