NATURAL HISTORY. 13 



arising from their being further compounded ; such as forming a neutral 

 salt, which becomes a species from its peculiar properties. 



A watch is a species of instrument for dividing time, whatever ma- 

 terials it maybe composed of; and though a watch is indivisible, yet it 

 has relationships, such as to a clock or a dial. The relations according 

 to their affinity are also to be classed, which constitutes a genus ; there- 

 fore we have to every species a genns. A ' divider of time' is a genus, 

 and genera form tribes, &c. Perhaps colours would illustrate this 

 doctrine as well as any subject. There are three primitive colours, and 

 by uniting these by equal proportions they appear to give fresh pri- 

 mitive colours, but which arise from the combination ; and by mixing 

 them in various proportions all the varieties of colours are produced. 



If we consider the vast extent of properties arising from the various 

 combinations of ten numbers, or the immense variety of ideas expressed 

 by twenty-four letters, we must see that very few primitives may pro- 

 duce a vast variety of properties arising from their various combinations. 

 Although all these divisions are not applied to matter in common, yet 

 they are as proper for matter at large as for those substances to which 

 they are applied. 



Animal matter is what I should call a species ; not as matter simply, 

 because it is probably the greatest compound we have, but from its 

 properties as a combination. The genus may comprehend only the 

 vegetable and animal [species of matter]. 



In my Lectures on Surgery I began with distinguishing the difference 

 between vegetable matter and animal matter, and also the matter of 

 the globe ; saying, that common matter had undergone a very consi- 

 derable change in producing the vegetable and the animal, in which 

 was not to be found a particle of any species of common matter, there- 

 fore an entire new arrangement or combination of common matter ; but 

 that they had sprung from common matter, were supported by it, and 

 returned to it again. 



This was with a view to make our distinctions hi the actions of the 

 body more accurate ; distinguishing with more precision between the 

 actions of animals, the decompositions and combinations of common 

 matter which are chemical, and the operation of combinations of com- 

 mon matter on each other, which is mechanical. Also to show that the 

 vegetable and animal had powers and modes of action totally different 

 from those of common matter, either in its chemical or mechanical 

 operations, and which depended upon their combination with the living 

 principle ; the whole operations of Nature appealing thus to consist of 

 a chain of four links. 



I observed that animals were formed from and supported by vegetable 



