PREFACE. 



AN important improvement in liistological technique, made 

 known since the publication of the last Edition, has been 

 effected by GILSON'S new mounting media. For these media 

 camsal balsam and euparal afford a ready and safe means of 

 mounting direct from alcohol, without the intervention of 

 essential oils or other clearing agents, which are of ten contra- 

 indicated; and of conferring on unstained or insufficiently 

 stained elements just the required degree of visibility, thus 

 enabling us to see details which are invisible in the usual 

 mounts. 



Some important improvements have also been made in the 

 silver fibril stains of BIELSCFOWSKY and RAMON Y CAJAL, which 

 have now become less capricious methods for the study of 

 neurofibrils, and valuable aids to the study of other objects. 

 I have given these methods at length, abstracting the whole of 

 RAMON'S methods from the latest original source. The sec- 

 tions relating to neurofibrils are thus almost entirely re-written, 

 and so are those relating to blood and blood-parasites. 



If these are the only novelties of much importance that 

 have offered themselves, yet I have found a large amount of 

 less important matter that it has seemed desirable to include 

 (the Index shows more than 700 new entries). I have been 

 able to find room for this, without increasing the size of the 

 book, partly by striking out some superfluous matter (mostly 

 of merely theoretical interest), and partly by rigorous con- 

 densation of the text and not a little typographical compres- 

 sion. To my satisfaction I find that this condensation and 

 compression is not to be regretted, for the text has in many 



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