PREFACE. Vll 



not yet sufficiently deeply felt as to have led to the 

 general lengthening of the period of undergraduate 

 study ; so that very little time is usually at the dis- 

 posal of medical students for collateral reading, or 

 for the pursuit of elaborate practical investigations. 

 It is desirable, moreover, since the laboratory time 

 itself is usually limited, to occupy as little of it as 

 may be, in oral descriptions of tissues and methods. 



It is these considerations which seem to justify the 

 addition of another to the long list of elementary 

 text-books. 



There are many points in this, as in every develop- 

 ing science, which are still unsettled opinion in re- 

 gard to them changing or being modified as new 

 facts and investigations are recorded. These have 

 been treated, for the most part, very briefly in the 

 text, it being left for the supplementary oral instruc- 

 tion to enlarge upon and explain them, as the light 

 thrown upon each by new researches may seem to 

 require. 



In the simpler form of " Notes on the Practical 

 Course in Normal Histology," the substance of this 

 book has been in use for two years in the laboratory 

 of the Alumni Association of the College of Phy- 

 sicians and Surgeons, and it has been found that, 

 with some preliminary preparation of tissues by the 

 instructor, the subject essentially as presented here 

 can be embraced in a course of forty lessons of about 

 two hours each. 



