Comparative Physiology. 191 



to trace the connecting links in both, from the lowest up to the 

 highest forms, and from the commencement of repi'oduction up 

 to maturity. It has been thought by DeCandolle, Fries, and 

 many others, that the best view of the subject is to study the 

 function in its most complete form, in the highest classes of 

 beings : but Dr. Carpenter gives good reasons for the oj)posite 

 opinion ; it is in the lowest forms of organised beings, and at 

 the commencement of life, that the performance of the function 

 is seen in its most simple condition, and the most complete 

 knowledge attained of what is essential and indispensable in its 

 due performance. 



In the Preliminary Remarks in the Introduction, he com- 

 mences by stating that Physiology regards the functions or 

 actions of living beings, and notices the difficulties attending 

 the investigations of physiologists. " The chemist, when de- 

 sirous of establishing to which of the ingredients in a given 

 mixture a particular effect is due, places each separately in the 

 conditions required to produce the result ; while the physiologist 

 finds that the attempt to insulate any one organ, and to reduce 

 the changes performed by it to definite experimental inves- 

 tigation, necessarily destroys or considerably alters those very 

 conditions under which its functions can be normally performed." 

 This is the fruitful source of error in all physiological expe- 

 riments, and the cause why practical experiments on a large 

 scale are so necessary to corroborate and confirm the de- 

 ductions of theorists. Many theories, which from the illustrious 

 names by which they were brought forward appeared to carry 

 a warrant with them, have not been found to stand the test of 

 experience. The operations of nature, though simple, are so 

 many and complicated that some very minute, though im- 

 poi'tant, circumstances have escaped observation. Portions of 

 organs are more easily insulated in the Vegetable Kingdom, and 

 he recommends therefore to commence with it, where the 

 simplest manifestation of the functions of the lowest grades of 

 organised beings enables us to comprehend and explain the 

 complicated phenomena of the highest. 



On organised structures in general, he regards inorganic or 

 mineral substances as held in connexion by electrical attraction 

 merely, every particle possessing a separate individuality. They 

 may be decomposed as organised substances, but not to the 

 same extent. " It may be regarded as the peculiarity of an 

 organism, that all its distinct parts, in their own way, subserve 

 a general purpose, and conduce to the maintenance of one 

 whole. The individuality of a mineral resides in each molecule ; 

 that of a plant (or inferior animal) in each member, and that of 

 one of the higher animals in the sum of all the organs. Change, 

 in organised bodies, is essential to our idea of life, and is the 



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