CHAPTER IX 



CLASS DEMONSTRATIONS IN HISTOLOGY AND 

 EMBRYOLOGY 



APPARATUS AND MATERIAL FOR THIS CHAPTER 



Demonstration microscopes, simple and compound (Figs. 195-196); Traveling 

 microscope (Fig. 197-198); Indicator ocular (Fig. 199-201); Marker for putting 

 rings around the parts of specimens to be demonstrated ( Fig. 61 ); Projection mi- 

 croscope (Fig. 207); Projection objectives (Fig. 211-212); Episcope (Fig. 214). 



DEMONSTRATION MICROSCOPES AND INDICATORS 



§ 393. Simple Microscope. — The simple microscope held in 

 one hand and the specimen in the other, has always been used for 

 demonstration, but for class demonstration it is necessary to have mi- 

 croscope and specimen together or the part to be observed by the class 

 is frequently missed. Originally blocks of various kinds to hold both 

 microscope and specimen were devised, but within the last few years 

 excellent pieces of apparatus have been devised by several opticians for 

 the purpose. The accompanying figure shows one of the best forms. 



Fig. 195. Simple Demonstra- 

 tion Microscope of Leitz ( Win. 

 Krafft, N. Y. ) As shown in 

 the figure this consists of a 

 handle, a stage and a lens holder 

 which slides up and down for 

 focusing. Fot observation the 

 student holds it up to the light. 



195- 



§ 394. Compound Demonstration Microscope. — This was 

 originally called a clinical or pocket microscope. It is thus described 

 by Mayall in his Cantor Lectures on the history of the microscope : "A 

 small microscope was devised by Tolles for clinical purposes which 

 seems to me so good in every way that I must ask special attention for 



