CLASS DEMONSTRATIONS 



[CH. VII 



THE PROJECTION MICROSCOPE 



270. Projection Microscope. One of the most useful and 

 satisfactory means at the disposal of the teacher of Microscopic 

 Anatomy and Embryology for class demonstrations is the Projection 

 Microscope. With it he can show hundreds of students as well as 

 one, the objects which come within the range of the instrument. 



It is far more satisfactory than microscopic demonstrations, for 

 with the projection microscope the teacher can point out on the 

 screen exactly the structural features and organs 'which he wishes 

 to demonstrate, and he can thus be certain that the students know 

 exactly what is to be studied. Unless one employs a pointer ocular 

 (Fig. 153), there is no certainty that the student selects from the 

 multitude of things in the microscopic field the one which is meant 

 by the teacher. Like all other means, however, the projection 



FIG. 158. Diagram of Adams' Solar Microscope. This illustrates well 

 the advantage of some form of projection microscope for demonstration pur- 

 poses. 



a, b, c, d, <?, f. Rays from the sun striking the mirror A-B, and being re- 

 flected horizontally to the condensing lens C-D. The condensing lens concen- 

 trates the light upon the object E-F. From the object the light passes to the 

 objective G-H. The objective then projects an enlarged image [-K upon the 

 screen at L-M. N-O opening in the shutter. 



The action is exactly like that of a magic lantern except that an object is 

 used instead of a lantern slide, and the objective gives a greater magnification 

 than the one used on a magic lantern. (From George Adams Essays. 1787.} 



