52 ON THE STUDY OF ZOOLOGY 



doctrine of nature, and is not very appropriately applied to 

 that limited division of natural science, which has for its 

 object the various forms and phenomena of life, the condi- 

 tions and laws under which this state exists, and the causes 

 which are active in producing and maintaining it. A foreign 

 writer * has proposed the more accurate term of " biology," 

 or science of life. 



Life, using the word in its popular and general sense, 

 which at the same time is the only rational and intelligible 

 one, is merely the active state of the animal structure. It 

 includes the notions of sensation, motion, and those ordinary 

 attributes of living beings which are obvious to common 

 observation. It denotes what is apparent to our senses ; 

 and cannot be applied to the offspring of metaphysical 

 subtlety, or immaterial abstractions, without a complete 

 departure from its original acceptation — without obscuring 

 and confusing what is otherwise clear and intelligible. 



The close connexion between life and respiration has not 

 escaped the notice of ordinary observers — of those who 

 were ignorant of anatomy and physiology. Hence the breath 

 has been popularly deemed the mark of life. The Latin 

 anima, or ' breath,' (from the Greek a»H^o?, ' wind'), was 

 also used to express the vital principle ; the essence of life 

 being supposed identical with the breath. But in the 

 phrases, ' animam efflare,' ' exspirare,' &c. the word seems 

 to be used in its original sense. In the same way, the Latin 

 spiritiis, or original of our spirit, from spiro, ' to breathe,' 

 means merely 'breath :' the same is the case with the Greek 

 TTUBvixoc : and this is the original sensible object, out of which 

 all the abstractions and fancies, all the verbal sophistry and 

 metaphysical puzzles about spirit, have proceeded. 



Anatomy and physiology should be cultivated together : 

 we should combine observation of the function with exa- 

 mination of the organization. The subjects are often dis- 



* G. R. Treviranus of Bremen, whose Biologie, oder Philosophe der 

 Lebenden Natur fur Natiirforscher und Aerzte, in 5 vols. 8vo. but not yet 

 finished, is a very interesting work, both for the philosophic plan on which 

 it is founded, and the original views with which it abounds. 



