WITH THE MICROSCOPE. 3OQ 



The philosopher and the fact-hunter seem to have discovered that 

 they may keep their offices quite distinct and yet work to each 

 other's great advantage. A compact seems to have been entered 

 into. The fact-finders consenting to act as the servants or tools of 

 the philosopher, provided he publicly acknowledges the high value 

 of fact-hunting, and spreads the fame of the fact-finder as well as his 

 own. Different schools of philosophy require differently constituted 

 fact-finders, and as each new philosophy rises in popular favour, its 

 own proper fact-hunters acquire the much-desired notoriety. 



But do not many errors now pass current as observed facts, and 

 do not many false generalisations interfere with the advance of real 

 knowledge ? Must not this be the case, if those who advance generali- 

 sations refuse to investigate for themselves, and practical observers 

 confine themselves to mere observation and refrain from thinking and 

 speculating concerning the facts they discover ? Disadvantage to both 

 must result from the attempt to draw a hard line between speculative 

 thought and practical work. Useful hypotheses are much more 

 likely to emanate from sound practical observers and experimenters 

 than from purely speculative thinkers, who are obliged to obtain all 

 their facts second-hand, and whose training has in too many instances 

 been such as to render them quite incapable of distinguishing real 

 facts from apparent facts, or of estimating the value or worthlessness 

 of the evidence adduced in favour of the accepted interpretation of 

 a particular appearance observed. 



In the hope of encouraging students to think as well as work, I 

 have ventured to offer many theoretical remarks in my book, though 

 it is mainly devoted to practical subjects, and has been written with 

 a strictly practical object. Though the speculations may soon have 

 to yield to others, they will not be altogether useless and will at any 

 rate afford some little interest, and I hope, stimulus, to those who do 

 not find pleasure in mere laborious aimless observation. 



In many parts of this book I have drawn attention to the great 

 importance of special methods of preparing tissues. But in order 

 to compare different textures with one another and the same texture 

 at different periods of its growth, a uniform process of preparation 

 must be adopted, or, in other words, all must be subjected to exami- 

 nation under precisely similar conditions. It has been shown that 

 all textures may be easily manipulated and examined under the 

 highest powers when immersed in glycerine, and that in every tissue 

 obtained from a living being, part is deeply stained while part is left 

 colourless, although it has been freely traversed by an aikiline colour- 

 ing matter in solution, p. 107. The first exhibits certain common 

 characters throughout nature, while the latter differs extremely in 



