1648 



Journal of Applied Microscopy 



A Demonstration Eyepiece — A Desideratum. 



Almost every teacher has experienced the difficulty of demonstrating objects 

 under the microscope to the student. The apparent size of objects under the 

 microscope is so much a personal matter and the appearance of so many objects 

 more or less confusing that the beginner is often found, after five minutes enthu- 

 siasm, to have observed the wrong object. The study of moving protozoa, 

 bacteria, etc., increases the difficulty. 



Usually some landmark is selected with which to call the student's attention 

 to the object he is to see. Even then it takes a good deal of alternate looking 

 by teacher and student until the particular point is satisfactorily made out. A 

 sketch is generally used with which to point out the desired features, but this 

 will not serve for moving objects or views that can be obtained only at intervals. 

 Besides, the student remembers the drawing better than he does the actual 

 object. 



These difficulties could be, to a great extent, overcome by what might be 

 called a demonstration eyepiece, — an eyepiece so constructed that both student 

 and instructor see the image at the same time. The need of such an instrument 

 has frequently been felt by the writer, and if it can be made practicable, no doubt 

 others would use it. The idea, in its first inception, is here given. 



I : 



iZ'-IJ. 





A Demonstration Eyepiece. 



The device consists of an ordinary eyepiece with cross-hairs for pointing 

 out the object. A prism above the eyepiece is so placed as to reflect the image 

 through a tube at right angles to the eyepiece to another prism at the end of 

 the tube. This prism will reflect the image upward into the eye. 



Now the instructor can point out the pseudopodia of an amoeba as they are 

 formed, the nucleus and the pulsating vacuole, or if the student is just beginning 

 he may be shown the value of focusing. Such an instrument might also be used 

 to test the student's knowledge of certain sections by having him point out and 

 explain the structures — both instructor and student looking at the same time. 

 Detroit High School. L. MuRI'.ACH. 



