THE 



GARDENER'S MAGAZINE, 



AUGUST, 1843. 



ORIGINAL COMMUNICATIONS. 



Art. I. Comparative Physiology. By R. Lymburn. 



{Continued from p. 352.) 



In Chap. III., On the Laws of Organic Developement, Dr. Car- 

 penter remarks " that, though the labours of the naturalist and 

 comparative anatomist have not yet established laws of the 

 highest degree of generality, yet many subordinate principles 

 have been based on a solid foundation, and many at first doubtful 

 are daily receiving fresh confirmation. The most important 

 part of the process of induction consists in seizing upon the pro- 

 bable connecting relation, by which we can extend what we 

 observe in a few cases to all. In proportion to the justness of 

 this assumption, and the correctness of our judgement in tracing 

 and adopting it, will the induction be successful. The more 

 extensive the acquaintance with nature, the more firmly is the 

 belief impressed that some relation must subsist in all cases, 

 however little we may be able to trace. It was formerly cus- 

 tomary to regard similarity of external form and evident pur- 

 pose as indicating the analogies between different parts, but the 

 developement of the functions is often found to originate in 

 sources entirely different. The wings of birds, &c., are formed 

 by expansions of the general integument over the anterior parts 

 of the osseous system, while in insects they are formed by prolon- 

 gations of the respiratory apparatus. In vegetables, the tendril is 

 developed in the vine from the peduncle or flower-stalk ; in the 

 pea, from the petiole or leaf-stalk ; in Gloriosa, from the point of 

 the leaf; and, in the singular genus Strophanthus, from the 

 point of the petal. Function, therefore, is not dependent on 

 developement, nor on structural analogy. There is little re- 

 semblance between the gills of a fish and the lungs of a qua- 

 druped, or the air tubes ramifying through the structure of an 

 insect; and those who are in the habit of forming exclusive 

 notions upon a hasty survey might be led to deny that any 

 3d Ser. — 1843. VII I. c c 



