ANIMALS AND PLANTS. 15 



CHAPTER II. 



ANIMALS AND PLANTS. 



THE division of living bodies into animals and plants rests on a series 

 of ideas early impressed on our minds. In animals we observe free 

 movements and independent manifestations of life, arising from 

 internal states of the organism, which point to the existence of 

 consciousness and sensation. In the majority of plants, which pass 

 their lives fixed in the earth, we miss locomotion and independent 

 activities indicative of sensation. Therefore we ascribe to animals 

 voluntary movement and sensation, and also a mind which is the seat 

 of these. 



Nevertheless these conceptions apply only to a proportionately 

 narrow circle of organisms, viz., to the highest animals and plants. 

 With the progress of experience, the conviction is forced upon us 

 that the traditional conception of animals and plants needs, so far 

 as science is concerned, to be modified. For although we find no 

 difficulty in distinguishing a vertebrate animal from a phanero- 

 gamous plant, still our conceptions do not suffice when we come to 

 the simpler and lower forms of life. There are numerous instances 

 amongst the lower animals in which power of locomotion and distinct 

 signs of sensation and consciousness are absent ; while, on the other 

 hand, there are plants which possess irritability and the power of free 

 movement. Accordingly the properties of animals and plants have 

 to be compared more closely, and at the same time the question has 

 to be discussed, whether there are any absolute distinctive characters 

 which sharply separate the one kingdom from the other. 



1. In their entire form and organization there seems to be an 

 essential contrast between animals and plants. Animals possess a 

 number of internal organs of complicated structure, lodged within a 

 compact outline ; while in plants the nutritive and excretory organs 

 are spread out as external appendages, with a considerable superficial 

 extension. In the one case there is found an inner, and in the other 

 an outer position for the absorbent surface. Animals have a mouth 

 for the entry of solid and fluid nutritive matters, which are digested 

 and absorbed in the interior of an alimentary canal, into which open 

 various glands, (salivary glands, liver, pancreas, etc). The useless 

 solid remains of the food pass out through the anus as faeces. 

 The nitrogenous waste material is excreted by a special urinary 



