REGARDED AS A MASS. 11 1 



with its own fellow ; or to distribute them into suitable pairs 

 by any other selection than that which obtains. 



This regularity of the animal structure is rendered more 

 remarkable by the three following considerations. First, 

 the limbs, separately taken, have not this correlation of 

 parts ; but the contrary of it. A knife drawn down the 

 chine cuts the human body into two parts, externally equal 

 and alike ; you cannot draw a straight line which Avill di- 

 vide a hand, a foot, the leg, the thigh, the cheek, the eye, 

 the ear, into two parts equal and alike. Those parts which 

 are placed upon the middle or partition line of the body, or 

 which traverse that line, as the nose, the tongue, the lips, 

 may be so divided, or, more properly speaking, are double 

 organs ; but other parts cannot. This shows that the cor- 

 respondency which we have been describing, does not 

 arise by any necessity in the nature of the subject ; for, if 

 necessary, it would be universal, whereas it is observed only 

 in the system or assemblage ; it is not true of the separate 

 parts ; that is to say, it is found where it conduces to beau- 

 ty or utility ; it is not found, where it would subsist at the 

 expense of both. The two wings of a bird always corres- 

 pond ; the two sides of a feather frequently do not. In cen- 

 tipedes, millepedes, and the whole tribe of insects, no two 

 legs on the same side are alike ; yet there is the most exact 

 parity between the legs opposite to one another. 



2. The next circumstance to be remarked, is, that, whilst 

 the cavities of the body are so configurated, as externally, 

 to exhibit the most exact correspondency of the opposite 

 sides, the contents of these cavities have no such corres- 

 pondency. A line drawn down the middle of the breast 

 divides the thorax into two sides exactly similar ; yet these 

 two sides enclose very different contents. The heart lies 

 on the left side ; a lobe of the lungs on the right ; balancing 

 each other, neither in size nor shape. The same thing 

 holds of the abdomen. The liver lies on the right side, 

 without any similar viscus opposed to it on the left. The 

 spleen indeed is situated over against the liver ; but agree- 

 ing with the liver, neither in bulk nor form. There is no 

 equipollency between these. The stomach is a vessel, both 

 irregular in its shape, and oblique in its position. The fold- 

 ings and doublings of the intestines do not present a parity 

 of sides. Yet that symmetry which depends upon the cor- 

 relation of the sides, is externally preserved throughout the 

 whole trunk ; and is the more remarkable in the lower parts of 

 it, as the integumonts are soft ; and the shape, consequent- 



