32 THE MICROSCOPE. [iNTROD. 



the observer himself, in this kind of investigation, than in almost 

 any other. 



The great impediment to deriving correct inferences from micro- 

 scopical observations has arisen from the discordance, too apparent, 

 in the narrations of different observers. This discordance has been 

 the result of a twofold cause ; namely, imperfection of the instru- 

 ments, and the very unequal qualifications of different observers. 

 The former cause is now almost completely removed ; the latter 

 must remain, while men imperfectly appreciate their own abilities 

 for particular pursuits. 



To make microscopical observation really beneficial to physiolo- 

 gical science, it should be done by those who possess two requi- 

 sites : an eye, which practice has rendered familiar with genuine 

 appearances as contrasted with those produced by the various 

 aberrations to which the rays of light are liable in their passage 

 through highly refracting media, and which can quickly distinguish 

 the fallacious from the real form ; and a mind, capable of detect- 

 ing sources of fallacy, and of understanding the changes which 

 manipulation, chemical reagents, and other disturbing causes may 

 produce in the arrangement of the elementary parts of various 

 textures. 



To these we will add another requisite not more important for 

 microscopical than for other inquiries ; namely, a freedom from 

 preconceived views or notions of particular forms of structure, and 

 an absence of bias in favour of certain theories, or strained analo- 

 gies. The history of science affords but too many instances of the 

 baneful influence of the idola specus upon the ablest minds ; and it 

 seems reasonable to expect that such creatures of the fancy would 

 be especially prone to pervert both the bodily and the mental 

 vision, in a kind of observation which is subject to so many causes 

 of error, as that conducted by the aid of the microscope. 



Finally, the sagacious Haller perceived, how necessary to the 

 furtherance of physiology is a knowledge of Organic Chemistry; 

 and we could adduce many instances to prove, that the atten- 

 tion which has of late years been paid to this subject, has not 

 been without its fruit, in giving us an insight into the nature 

 of many functions, which, without it, we could not have 

 obtained. 



In the living body the most delicate chemical processes are un- 

 ceasingly going on, for the formation of new compounds and the 

 destruction or alteration of old ones. It is evident that no progress 

 can be made in the investigation of these invisible processes, unless 



