178 REPRESENTATION OF THE 



ence of a distinct topical life. The liairs and teeth of ani- 

 mals generally, and the antlers of the deer, have already 

 been cited as furnishino: illustrations of it. The first set of 

 teeth, for instance, are formed each in its own capsule by a 

 process of local growth, quite independent of that of the 

 neighbouring tissues, nay, in so far opposed to it, that at a 

 certain stage of development the integuments of the gum 

 are partially disintegrated to allow of their eniption. A 

 tooth, thus geiierated by independent growth, some time 

 after attaining maturity, undergoes a process of decay, end- 

 ing in its ultimate removal, when a new tooth of the second 

 dentition takes its place by a similar process of local gTO\^i;h. 

 In its turn this tooth also is shed, and though in most 

 species it has no successor, yet in a few there is a constant 

 succession durins: the whole lifetime of the animal ; and 

 this is the general rule in the case of the hair.* Hence in 

 such local formations as teeth, hair, &c., we have, in the 

 way they are marked off from the neighbouring parts, and 

 in this succession of growth, maturation, a] id decay — re- 

 peated again and again, and epitomizing, as it were, the life 

 of the animal on which they gTow — evidence of a vitality, 

 quite as defined perhaps in itself as that presented by the 

 free zooids of the lower species, though their functional 

 dependence on the common circulation, and the mechanical 

 bond of a common integniment, prevent their exhibiting the 

 more obvious phenomena of a separate life. But as we 

 descend in the scale of organization we come to species, 

 where, from the absence of centralizing influences, the se- 

 veral organs — which are possessed of a vitality, less ener- 

 getic perhaps, but more enduring than in the higher — be- 

 come emancipated, as it were, from the control of the 

 general system, and appear as zooids, that is, in the guise 



* Paget' s Lectures on Sm-gical Pathology. Kirkes' Handbook of 

 Physiology, Ch. X. 



