The Microscope. 177 



been able to distinguish the pollen grains in pure honey, while they 

 are absent in artificial honey and only sparingly present in adulter- 

 ated honey. The pollen grains vary considerably in size, but are 

 easily distinguished with a 4-10 inch objective. The members of 

 the club will examine the honey for sale in St. Louis, and report at 

 the next meeting. 



One of the Griffith Club microscopes was shown, and admired 

 by all. 



The next meeting occurs June 5. 



ELEMENTARY DEPARTMENT. 



A COURSE IN ANIMAL HISTOLOGY. 



FRANK W. BROWN, M. D. 



THIRD PAPER. 



XJLOOD. — As blood-cells are exceedingly delicate, great care 

 should be taken in their examination. When removed from 

 the circulation they quickly undergo various changes, even when no 

 reagents are brought in contact with them. To study them satisfac- 

 torily requires that their preparation for examination should be 

 rapidly performed and that the specimens should be frequently 

 changed for fresh ones. Reagents, excepting those required to 

 'develop' certain structures of the cells, should be avoided. The most 

 simple method is, of course, to place a drop of fresh blood on a 

 slide, cover and examine. When this is done, however, little can be 

 seen as the corpuscles will be found packed together, and in several 

 layers. A neat method for avoiding this condition has been sug- 

 gested by Prof. Stowell. It is as follows : the surface of a glass 

 slide is gently breathed upon and a drop of fresh blood is brought in 

 contact with the slightly moistened surface. One surface of the 

 cover-glass is now breathed upon and immediately its edge is placed 

 close to, just in contact with the edge of the drop of blood. With 

 the aid of a needle, the cover is lowered away from the drop, not 

 over it, until it touches the slide. The blood corpuscles will immed- 

 iately flow between these moist glasses by capillary attraction until 

 the surface beneath the cover-glass is nearly or entirely covered. 

 Prepared in this way it will be found that there is but a single layer 

 and that the corpuscles are not crowded together. Such a prepara- 



