THE MICROSCOPE. 197 
_ fresh material is subjected to the action of the potash solution, the 
spermatozoa die with their tails coiled up. To prevent the coiling 
I allowed a specimen to die at the ordinary temperature of the at- 
mosphere, which will usually take about thirty-five hours, though 
the weaker ones will drop off in five or six hours. By the time 
they all are dead, the specimen will be swarming with bacteria. 
To avoid bacteria, | placed a specimen in an ordinary ice-box, 
' where I supposed they would die in less than an hour, but to my 
great astonishment they were as lively after being twenty-four 
hours on the ice as when first placed there, not one dead or motion- 
less was to be seen. Replacing the specimen in the ice-box for an- 
other twenty-four hours, I found at the end of that time that some 
of the spermatozoa were dead, but still quite a large number were 
swimming about. 
Later I bored a hole in a block of ice, and into this dropped a 
vial containing a specimen. I examined this once an hour for fif- 
teen hours, with much the same result as obtained from the ice-box 
lot. 
A specimen kept warm, but at a temperatuae something below 
that of the human body, died in about five hours, hence I con- 
cluded that cold water, used as a destructive agent, preserves the 
spermatozoa, but that moderately hot water would kill the most of 
them. 
When mixed with water the spermatozoa may be stained any 
desirable color ; or by using red first, followed by green, the bodies 
appear red and the tails green. When the stains have taken effect, 
a plug of absorbent cotton may be placed in the neck of a funnel, 
and the specimen filtered through it. If the plug be tight enough, 
so that the water will not stream but only drop through it, thous- 
ands of the objects pass through, but tens of thousands remain in 
the cotton This plug is then taken out and the water squeezed 
from it. Place a slide on the turn table, dip an artists’ small red 
sable brush into the fluid squeezed from the plug, and while the 
turn table is in motion bring the point of the brush to the center of 
the slide. A small round deposit will be left, which should be 
dried. Next with white zinc cement, make a ring of about half an 
inch in diameter on the slide, allow this to dry for a couple of days 
and then slightly moisten the ring with the same cement, lay on a 
cover glass, and you have a permanent mount. 
