2nfl THE AMERICAN MONTHLY [Oct 



Notes on Microscopy. 



JOHN. H. COOKE, F. h. S., F. G. S. 



Blood. — Permanent preparations of blood — amphibian 

 for preference as the red cells are so large and contain 

 such prominent nuclei — may be prepared by allowing 

 fresh blood to fall drop by drop into a solution of osmic 

 acid (two per cent acid solution, one part ; one per cent so- 

 lution of sodium chloride, two parts ; distilled water one 

 part). The solution should be constantly stirred while the 

 blood is dropping. Allow the blood and acid to stand one 

 night, and then wash the acid away with distilled water. 

 Add alcohol, then clove oil, in which the blood may be 

 kept indefinitely. Before the alcohol is added, the nucleus 

 of the corpuscle may be stained in alum-carmine ; or the 

 whole corpuscle may be stained in aniline blue. Mount in 

 balsam. 



Warm Slide. — A warm slide is an indispensable piece 

 of apparatus to the student of histology. In the stud}' of 

 am£Bboid movements it is essential unless a suitable spot 

 in the frog's web can be found. To make a warm stage, 

 take a strip of copper the size of a glass slide, and make 

 a diaphragm openinc^ in the centre. Attach a long strip 

 of copper to this — or the whole can be of one piece — suf- 

 ficient to project about four inches over the edge of the 

 stage of the microscope. The flame of an alcohol lamp 

 heating the end of this strip will, by conduction, heat the 

 whole piece together with the slide placed on it. A drop 

 of blood being prepared for examination in the usual way, 

 make a ring round the cover-glass with oil to prevent 

 evaporation, place on the warm stage, apply the heat, and 

 the leucocytes can be studied in their movements with 

 higherpowersand with greater ease thanin the frog's web. 



Water Baths. — A water bath is another very neces- 

 sary adjunct where a certain very moderate degree of heat 

 is not to be exceeded. Few persons fully appreciate the 



