386 Analog^/ between Vegetables and Animals 



other. On the opposite hand, the line of demarcation between 

 plants and animals we find it extremely difficult to trace, for 

 the individuals belonging to these two kingdoms approach 

 each other so closely, both in their organisation and their 

 functions, that it is next to impossible to describe their respec- 

 tive characteristic features. To so great an extent is this cor- 

 rect, that there are many substances having qualities so peculiar, 

 that philosophers can scarcely determine whether they belong 

 to the vegetable or to the animal part of creation. Zoophytes, 

 for instance, were considered by Ray and Lister as vegetables ; 

 but they are now regarded as productions of the animal king- 

 dom. The object of the present essay is to describe the 

 structure and functions of vegetable bodies, and to endeavour 

 to point out in what respects they resemble, and in what they 

 differ from, those of animals. 



The first and most essential mark of resemblance that 

 appears to exist between the vegetable and animal kingdoms 

 is the possession of life. With this principle they are both 

 equally endowed, and by its presence they are distinguished 

 from inorganic substances. What life is, I am unable to define ; 

 for all the researches of philosophers have hitherto proved 

 inadequate to discover in what it consists, or from what source 

 it springs. Some have conceived that it depended upon a 

 nicely adjusted combination, or a harmony of actions going 

 on between the different organs of a living being ; others have 

 supposed that it is an element residing in the blood ; and 

 others, again, have identified it with caloric, with oxygen, and 

 with electric fluid. If, however, we are ignorant of the nature 

 of life, and are incompetent to decide whether it be a real and 

 distinct agent or not, yet we are perfectly acquainted with the 

 phenomena that indicate its existence. Observation has taught 

 us that there are certain properties attached to living beings, 

 of which inorganic substances are totally destitute. We 

 observe, for instance, that the latter are incapable of assimi- 

 lating foreign materials to their own nature ; that their bulk 

 is enlarged only by the external accretion of new particles ; 

 that they are under the continual influence of physical agents ; 

 and that their destruction is never effected, except by some 

 mechanical force separating their integrant particles, or by 

 some chemical agent producing an alteration in the arrange- 

 ment of their ultimate elements. 



On the other hand, we perceive that organised beings have 

 the power of converting substances of almost every variety of 

 composition into the tissues which compose their organs ; that 

 they can resist, to a considerable extent, the action of the 

 ordinary laws of matter ; that they are produced, by the pro- 



