viii PREFACE 



most difficult part of the process. The printing was done in the same 

 way as in ordinary three-color work. Without the perfect negatives 

 made by Dr. Learning through absolutely correct color-filters and the 

 very intelligent and skilful work of the Colortype Company, the results 

 obtained would not have been possible, a fact emphasized by repeated 

 failures during many months of experimentation. The cost of the 

 three-color work has made but an insignificant addition to the price of 

 the book, while, it is believed, the color-illustrations have added greatly 

 to its practical value. 



Through the generous interest of the publishers in the manufacture 

 of the book, unusual care was bestowed on the two hundred and forty- 

 seven illustrations in the text. Of this number, one hundred and sixty- 

 five were selected from three hundred and sixteen that appeared in a 

 previous work. All, however, have been newly reproduced from the 

 originals. Ninety of the one hundred and sixty-five are from Sappey, 

 Bonamy and Beau, and Hirschfeld. These were imported from Paris 

 in 1874. They are not only highly illustrative, but are fine examples 

 of engraving on wood, now practically a lost art. Eighty-two figures, 

 including four in colors, are either original or are taken from modern 

 works. The latter could hardly be improved on by new drawings. 



Special mention should be made of four figures reduced from photo- 

 graphs in Dalton's Topographical Anatomy of the Brain, and six figures 

 reduced from photographs in the Atlas of the Karyokinesis and Fertili- 

 zation of the Ovum, by Professor Edmund B. Wilson, with the coopera- 

 tion of Dr. Edward Learning. A small edition of the late Professor 

 Dalton's work was printed in 1885. It is now a rare book and little 

 known ; but the prints represent the specimens with absolute fidelity, 

 and are quite as useful for purposes of study as actual sections. The 

 prints in Professor Wilson's Atlas are superb and unique. The figures 

 from these works have not before been reproduced. 



It may fairly be presumed that a considerable majority of English- 

 speaking medical practitioners and students for whom this work is 

 intended have been accustomed, by early education and common 

 usage, to English weights and measures. To such readers, the metric 

 system, now commonly used in scientific literature, frequently fails to 

 convey a definite idea without a mental reduction to the familiar stand- 

 ards. For this reason, English weights and measures and the Fahren- 

 heit scale are retained, and metric equivalents are given in parentheses. 

 The micron (yoVo" ^ a millimeter, or 2 SIJFO ^ an mcn )> indicated by /A, 

 is frequently employed. 



I am much indebted to qolleagues and others for aid in prepar- 

 ing illustrations, and extend to them my grateful acknowledgments : 



