PRELIMINARY DISCOURSES. XV 



office, during the existence of the animal: But the vessels of Plants 

 being directed to the exterior, there will be a constant possibility, 

 either of their being elongated, or of new ones being developed on 

 the outer surface. There will then, consequently, be a certain limit 

 to the growth of Animals; but none to that of Vegetables. There 

 will then, in Animals, be a death from old age ; which will happen 

 when the existing vessels not being capable of renovation shall 

 be obstructed by the influx and lodgment of the minute particles of 

 matter which are conveyed to them. This cause of death does not 

 occur in Vegetables at least, not in perennial vegetables, since 

 new vessels may be indefinitely developed, and take upon them- 

 selves the office of the old ones. Animals, therefore, die of old age, 

 or of accidents ; perennial Plants of accide'nts, only. 



In consequence of Animals having a centre of nutrition, and of 

 life, it follows that they can rarely, if ever, be divisible into several 

 individuals ; for those animals called Polypi which seem to be an 

 exception to this rule ought rather to be considered as aggrega- 

 tions of a number of individuals : Plants, on the contrary, having 

 no common centre and being endowed with the faculty of pro- 

 ducing new vessels to an indefinite extent may be divided without 

 loss of life, and can be indefinitely multiplied by cuttings.* 



From the general considerations thus presented, the following 

 Principles seem to result : 



1. That the differences between the two organized kingdoms 

 consist essentially in this, that one of them is endowed with sensi- 

 bility, and the power of voluntary motion, of which the other is 

 destitute. 



2. That the general office, or business of Plants in the great 

 system of a wise and beneficent Providence is to elaborate and 

 prepare inorganic matter, so that it may become fitted for the 

 nourishment of Animals :f and 



* This is more particularly true, however, in those plants which form buds, and 

 live more than a single season; for the buds of trees, and shrubs, may be regard- 

 ed as so many distinct Individuals, congregated on a common stock. Even those 

 perennials with herbaceous stems, which die down to the ground every winter, 

 form a kind of buds in the crown of the root (or rhizomd), from which proceed 

 the aerial stems of the ensuing summer. Those plants called annuals (which 

 germinate from the seed, bloom and perfect their fruit, and die, as it were a natural 

 death, within the year) rarely produce anything like buds : and are by no 

 means so susceptible of division, or multiplication by cuttings, as the woody 

 perennialt. 



t"It is one of the laws of nature that Animals shall feed on organized matter, 

 and Vegetables on unorganized. For the support of animal life, therefore, we 

 require vegetables to change the mineral constituents of the surrounding media 

 Into suitable nutriment." Prof. HA&VIY. 



