76 THE MICROSCOPE. May 
looking over a not large spread of fine material, on a slide 
magnified say 500 diameters. The labor required to go 
over the whole mass of detail with close attention, is con- 
siderable. We willtake a spread five-eighths of an inch 
square. This magnified 500 times would give 312 inches, 
or twenty-six feet square. Let the magnified field under 
close observation at one time be three inches square, the 
distance of the eye being ten inches. ‘This field will in 
practice be found to be really too large, when fine detail is 
scanned. The number of three-inch fields will be 10,816, 
which, run past at the rate of one a second, would take 
three hours.”’ 
Microbe Farming.—The mystery of nitrification is now 
so well-known that any farmer can understand it. Plants 
live in nitrogen, but apparently have no power to take it 
either from the air or the soil. Here the nitrogen bacteria 
get in their work. These microbes, like atomic sponges; 
take in the nitrogen from the soil and the air, and trans- 
form it into nitric acid, in which form the plant can con- 
sume it. A soil may be destitute of nitrogen and need 
both that and the microbes, or it may lack both that and 
the microbes, or it may lack only the microbes, in which 
case a supply of them renders the field immediately fertile. 
Stable manure has little nitrogen but swarms with the 
germs of microbes. Add to a field where clover seed 
wont ‘‘catch”’ a light dressing of soil from a plat where clo- 
ver thrives to perfection, and a catch of clover seed is al- 
most sure to result. Why? Because the soil added is 
full of the germs or microbes that enable the young 
clover plant to avail itself of the nitrogen in the ground or 
air.—Am. Agriculturist. 
A New Method of Staining Nerve Tissue.—Vastari- 
ni-Cersi (Rif. Med., Feb. 14, 1896) describes a new and 
effectual method of staining the spinal cord, etc., for micro- 
scopic purposes. The entire cerebro-spinal axis, with the 
meninges, is plunged into about 3 litres of an aqueous 
solution of formaldehyde (16 per 1,000). The tissue is 
left in the medium for two weeks; the meninges being re- 
