I 



PREFACE TO PART I. 





This, the third edition of "Notes on Microscopical Methods for the- Us< of Stu- 

 dents in the Anatomical Department of Cornell University," has been entirely 

 written, enlarged, and more fully illustrated; and while elementary matters have 

 received fuller treatment than in previous editions, in this, an especial (licit has 

 been made to give a more adequate account of Homogeneous Immersion < >h 

 ives, the Sub-Stage Illuminator. Camera Lucidas, the Micro Spectroscope and 

 Miero-Polariscope, that is to apparatus which is coming to be used more and more 

 in the higher fields of investigation in pure science and in practical medicine. 



It is thoroughly believed by the writer that simply reading a work on the micro- 

 scope, and looking a few times into an instrument completely adjusted by another, 

 is of very little value in giving real knowledge. In order that the knowledge shall 

 be made alive, it must be made a part of the student's experience by actual experi- 

 ments carried out by the student himself. Consequently exercises illustrating the 

 principles of the microscope and the methods of its employment have been made 

 an integral part of the work. 



In considering the real greatness of the microscope, and the truly splendid s< 

 ice it has rendered, the fact has not been lost sight of that the microscope is, after 

 all, only an aid to the eye of the observer, only a means of getting a larger in 

 on the retina than would be possible without it ; but the appreciation of this retinal 

 image, whether it is made with or without the aid of a microscope, must always 

 depend upon the character and training of the seeing and appreciating brain behind 

 the e3 r e. The microscope simply aids the eye in furnishing raw material, so to 

 speak, for the brain to work upon. 



The necessity for doing a vast deal of drudgery or "dead work," as it has be« D 

 happily styled by Prof. Leslie, before one has the training necessary for the appre- 

 ciation and the production of original results, has been well stated by Beale 

 "The number of original observers emanating from our schools will vary as | 

 tical work is favored or discouraged. It is certain that they who are most fully 

 conversant with elementary details and mo'st clever at demonstration, will he I 

 successful in the consideration of the higher and more abstruse problems, and will 

 feel a real love for their work which no mere superficial inquirer will experience. 

 It is only by being thoroughly grounded in first principles, and well practised in 

 mechanical operations, that any one can hope to achieve real success in the higher 

 branches of scientific enquiry, or to detect the fallacy of certain so-called experi- 

 ments." 



In preparing this manual it has been taken for granted that the student is al- 

 ready familiar with elementary physics, especially the subject of opti. 



The experiments iu micro-chemistry (Ch. V.) are given for the sake of practice 

 for the junior chemical students who take the course in order to gain a know! 

 of the microscope as an aid to chemistry. 



In Part II will be given the application of the microscope to study and investi- 

 gation in Vertebrate Histology. ^ )N in;NRV GAGE, 



Cornell University, 



October i, 1891. Itb — New York, U.S 



