iv Preface. 



tion of germs is not exhaustively discussed, and the 

 usual illustrations of bacteriological apparatus have 

 been omitted. 



As to the translation itself a few words are neces- 

 sary : Weights and measures, given in the metrical 

 system in the original, have not been changed. Di- 

 mensions which occur in this work are chiefly those 

 of microscopic objects which are now rarely ex- 

 pressed by American microscopists in fractions of an 

 inch. The thermometric readings are in all cases 

 given in the centigrade scale. For those who are 

 unfamiliar with the decimal system the Appendix 

 will supply the requisite information. 



The few foot-notes which I have introduced are in 

 some cases intended to be supplementary to the text, 

 referring to discoveries which have been made since 

 the publication of the original in 1891. In other 

 cases they are explanatory of words or statements 

 which might otherwise be misunderstood. 



To the illustrations which occur in the French 

 text I have added a few others borrowed from difler- 

 ent sources, which are acknowledged in the descrip- 

 tions accompanying the figures; four are from draw- 

 ings of preparations in my own possession. 



R. R. DiNWIDDIE. 



Fayetteville, Ark., July 10, 1894. 



