116 THE AMERICAN MONTHLY [Apr 



Preparing Isolated Slide.— This slide displays the great- 

 ly elongated branches of the cells better than when seen 

 in situ within the tissue of the spinal cord in ordinary prep- 

 arations. It was made by rubbing- the end of a segment 

 of the spinal cord of an ox across the slide,and then stain- 

 ing in haematoxylin, for 24 hours, all that has adhered to 

 the slide. It was then washed with alcohol, dehydrated, 

 cleaned with olive oil, and mounted in balsam. Besides the 

 branching of the nerve cells, there may be seen innumer- 

 able threads forming a dense tangle, in whose meshes are 

 many dark granules. The threads and granules, together 

 with a somewhat undifferentiated fluid-like substance seem 

 to form the intercellular neurogleaof the spinal cord. The 

 threads are not unlike the slender branches of the nerve- 

 cells,and the granules somewhat resemble their nuclei, and 

 it has been suggested by Dr. Carlier, of the University of 

 Edinburgh, that they are the remnants of degenerate cells. 

 The best group of cells may be seen by placing the slide 

 on the stage with the club label to the left, and searching 

 near the edge of the cover-glass at the spot here indicated 

 by a Cross. — B. L. Seawell. 



A Mount of Putrefactive Bacteria. — This specimen was 

 dried from water spontaneously, without heat, upon the 

 cover-glass, and then immersed for several hours in a mor- 

 dant composed of tannin thirty grains, anilin oil twelve 

 drops and alcohol one fluid ounce rendered slightly alkaline 

 with sodic hydrate ; and then, after soaking in water for 

 five minutes to remove excess of the mordant, it was stain- 

 ed with neutral solution of rosanilinor fuchsin. The fresh- 

 ness of this specimen which was prepared in 1891 shows 

 the value of mordanting for staining bacteria. The meth- 

 od doesnotdistort and shrink the forms as passing through 

 the flame does, the alcohol and tannin fixing the bacteria in 

 more natural shape than is accomplished by other methods. 

 The spiral forms showing flagella easily are spirillum un- 

 dula; the straight rods are bacillus ulnus, which also show 

 the flagella under a good l-10th or l-12th immersion objec- 

 tive. The dendritic forms on this slide are due to the tan- 

 nin, and not to the bacteria ; they may be avoided, but are 



