76 INTRODUCTION. 



same kind, which are previously developed: thus, in the 

 nervous system, the medulla, which is first developed, is more 

 symmetrical than the brain ; the ribs are less symmetrical than 

 the spinal column, and more so than the sternum. Finally, we 

 may further observe, that the parts are most symmetrical at the 

 period of their formation, and that this kind of regularity, 

 afterwards changes: the stomach, intestines and liver, are 

 less irregular at first, than at a later period; the vertebral 

 column, at first exactly median, gradually inclines to the left, 

 from the predominance of the right arm, and thence results 

 the inclination of the nose, the unequal elevation of the testi- 

 cles, the frequency of hernia on the right side, &c. Sometimes 

 such a derangement of this symmetry is observed, that the or- 

 gans of one side, occupy the other, and vice versa; this is called 

 a transposition of the viscera. In this case, which happens in 

 about one, of three or four thousand subjects, and that I have 

 seen four or five times, the trilobated lung, the liver and the 

 ca3cum, are on the left, while the bilobated lung, the apex of 

 the heart, the spleen, the sygmoid portion of the colon, &e. 

 are on the right: Individuals thus situated, are not, however, 

 left-handed on this account. The diseases, which affect the 

 symmetrical organs, and those whose seat is in parts that 

 are not so, present a very remarkable difference. It has been 

 even asserted, but upon hypothetical views, that each side of 

 the body, has a greater predisposition to certain maladies, than 

 its fellow.* 



Comparisons have also been established, and analogies sought 

 for, between the upper and lower halves of the body. The 

 analogy between the limbs is evident; the shoulders and pel- 

 vis, the leg and the arm, the hand and the foot, are construct- 

 ed on one plan, and differ only so far as their different func- 

 tions require. As to the analogy, supposed to have been 

 found in man, as in the articulata, between different sections 

 of his trunk, and between the limbs, and the jaws, it rests on 

 a comparison between objects too dissimilar to admit of it. 



Carried away by a forced analogy with the radiata, anato- 



* See Mehlis, de rnorbis Jiominis dextri et sinistri. Getting. 1818. 



