PREFACE TO THE THIRD EDITION. 



IN the present edition, the general plan of the work has not 

 been altered in any way ; and so far from attempting to enlarge 

 or elaborate the matter of the last edition, I have tried, when 

 practicable, rather to reduce or condense it ; for I am of opinion 

 that of all other books, the one designed as a text-book on a 

 scientific subject should be as free as possible from that obtrusive 

 prolixity or padding, which tends to influence in an unsatis- 

 factory way both the patience and pocket of the student. The 

 present edition is a trifle larger than the last, due to the 

 addition of a few small sections which appeared necessary, and 

 to the insertion of a number of extra cuts. The majority of the 

 added illustrations are electrotypes from Franck's edition of 

 Leyh's work, to the publishers of which, Messrs. Shickhardt & 

 Ebner, my acknowledgments are due, as also to Mr. Renshaw, 

 Messrs. Churchill & Co., and Messrs. Macmillan & Co., for various 

 cliches from the works of Milne Edwards, Huxley, and Mivart. 

 The plates will, I think, from an artistic point of view, be found 

 greatly superior to those of the second edition, they having been 

 engraved specially for the present one. 



I have received assistance, alike varied and valuable, from 

 Professor Lewis, of Edinburgh, which I beg here to ackoowledge, 

 and especially his trouble in drawing up and arranging the 

 article on foetal development the last in the book. Professor 



