90 The American Naturalist. [January, 
a little more distended than in the others. When first placed in the 
solution they gave off considerable slime, but this became perfectly 
transparent so, as noted by Blum, the form and colors of the animals 
were not obscured. 
With salamander blood some startling effects were obtained. A few 
drops of blood were placed on a slide in a 1 per cent. solution of for- 
maldehyde and watched under the microscope. The corpuscles and 
especially the nuclei were seen to swell rapidly. The nuclei became 
as large almost as the original corpuscles and were seen to pop out of 
the corpuscle like a grape from its skin. The envelopes then became 
very pale and finally disappeared from view, the nuclei, however, 
remained very distinct. Staining with Erlich-Biondi mixture showed 
that the body of the corpuscles had simply been rendered very trans- 
parent by the solution, while immersion in alcohol coagulated the 
fibrin into an opaque, straw-yellow mass, and brought the corpuscles 
faintly back into view. This explains the phenomenon of the return 
of the color of blood vessels noted by Blum as due to the coagulation 
of the fibrin which may also be stained somewhat by the color drawn 
from the corpuscles. The same experiment was performed with a 4 per 
cent. formaldehyde solution in place of the weaker one and the swelling 
effect found to be very much lessened, none of the nuclei becoming as 
large as the corpuscle nor escaping, otherwise the results were the 
same. 
After this an earthworm was anesthetized with chloroform, placed 
ina 1 per cent solution of formaldehyde for several hours and after- 
wards removed toa 2 per cent. solution. There it remained for an 
equal length of time, when it seemed perfectly hardened and was re- 
moved to Czoker’s alum cochineal. On the following day pieces were 
rapidly dehydrated in 70 per cent. and 95 percent. alcohol and imbed- 
ded in paraffin. Sections made from them showed all micro-anatomi- 
cal details perfectly preserved. Nothing had stained but the nuclei 
which had all become very much swollen, giving the whole section a 
bright red-purple appearance. So decidedly had they swollen that in 
both series of the muscular system, and in the septa where they are 
not ordinarily visible, nuclei were shown very distinctly and in large 
numbers. Careful observation showed the nucleolus a little more 
deeply colored than the rest, while the chromatic filaments seemed 
swollen and less distinct. 
Sections were also made of an earthworm hardened in pure formalin 
and no swelling whatever was to be noticed, while all cytological. 
detail was remarkably well preserved. 
