The Microscope. 277 



ST. LOUIS CLUB OF MICROSCOPISTS. 



' I HE oppressively warm weather did not prevent the members of 

 -*- this club meeting Tuesday evening, August 2, and holding a 

 va ry successful session. Specimens were exhibited by Mm. Uhardt, 

 Otto Meyer, J. C. Falk, E. T. Jester, A. J. Hoenney, Frank Davis, 

 and others. Among the objects examined were samples of pure 

 powdered drugs and spices, vegetable histological specimens, etc. 

 Professor H. M. Whelpley gave a short illustrated lecture on polar- 

 ized light. 



The club is collecting quite a cabinet of interesting specimens, 

 and intend to give a public entertainment this fall. The next regular 

 meeting will occur Tuesday evening, September 6. 



ELEMENTARY DEPARTMENT. 



SEVENTH LESSON. 



"cleanliness is akin to godliness." 



ly/fOUNTING-MEDIA.— Canada balsam is the one mounting- 

 -*-"-*- medium thus far employed in the working of these lessons 

 when a permanent preparation is desired. In the writer's experience 

 it is the only one which insures comparative permanency, and should 

 be used in preference to all others when admissable. Yet there are 

 occasions when a different medium will be found necessary, such, for 

 example, as in the mounting of fresh tissues or when stains have been 

 employed which would be injured by the balsam. All necessary 

 m^edia for use in preparing animal tissues will be found among those 

 here described. 



Canada Balsam. — The commercial balsam can be used without 

 further preparation, but, as it is veiy viscid, the addition of some 

 thinning agent, as suggested in the Fourth Lesson, page 172, will be 

 found advantageous. Chloroform or benzol may be used for this pur- 

 pose. Chloroform is rather better, as balsam prepai'ed with it does 

 not shrink so rapidly, thus avoiding vacuolations under the cover- 

 glass. When, however, it is desired to mount objects stained with 

 the anilin colors, benzol is to be chosen, as it does not act so destruc- 

 tively on these dyes as chloroform. A somewhat more elegant pre- 

 paration can be made by first heating the balsam over a water-bath. 

 This frees it from the turpentine and leaves it as a brittle mass. 

 This is then to be dissolved in chloroform, filtered and kept in a 



