ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
705 
worst. Secondly, independently of the extent to which this takes place 
there is generally a change of form. It appears impossible almost entirely 
to avoid this, but by most methods the rectilinear and angular outlines 
of life are replaced by pyriform, ovoid, spherical, or even oblate contours 
in the permanent preparations. It was experimentally shown that the 
extreme changes of cell form were not produced in alcohol, and further 
that in some sections of the best series stained on the slide in the ordinary 
way the cells suffered considerable distortion. The chief engine in 
distortion appears to be the passage from alcohol into benzole, chloroform, 
or turpentine, and vice versa. It may be noted that the tendency of all 
the cells to assume a drop-like form proves that the force which effects 
their distortion is surface-tension. It does not seem unlikely that the 
reduction in volume is due to the abstraction of water and soluble matters 
by alcohol. 
Preservation of Mammalian Brains by Eormol and Alcohol.* — 
Messrs. G. H. Parker and K. Floyd think that the advantages of the 
employment of formol in hardening the organs of the central nervous 
system over other reagents employed for similar purposes must be obvious 
to any one that has used it. A sheep’s brain, when placed in a 2 per cent, 
solution of formol, attains in the course of a week or ten days a remark- 
able degree of firmness and elasticity, while it preserves in great part 
its original form and colour. The only important defect is a marked 
increase in volume. With the object of correcting this defect the authors 
were led to experiment with other hardening fluids. Alcohol and formol 
appear to do well, and the following combination was found to meet 
requirements : — Alcohol 95 per cent., 6 volumes, formol 2 per cent., 
4 volumes. The formol employed was that sold by Merck of Darmstadt 
as formaldehyde 40 per cent. Owing to the rapidity with which this 
mixture penetrates tissues, the hardening of large, freshly prepared 
brains necessitates little more than simple immersion. Sheeps’ brains 
prepared in this way retain their original colour and form, and show 
almost no change in volume. 
Disinfectant Action of Formalin. f — The experiments made by Dr. 
G. Burckhard as to the disinfecting action of formalin showed that this 
fluid has strongly antibacterial properties, though the results did not 
come up to the expectations formed of it. The animals used were mice, 
pigeons, and rabbits, and the infecting minrobes, anthrax and the bacillus 
of fowl-cholera. The dead animals were placed on wadding soaked with 
formalin and covered with a bell-jar. This procedure was found to 
prevent or considerably retard decomposition. Experiments were also 
made as to the influence of formalin on the metabolic products of 
bacteria. For this purpose the bacillus of tetanus was employed. The 
products of a 10 days’ old bouillon culture were passed through a 
Beichel’s filter and injected subcutaneously into mice. It was found that 
while formalin possesses the power of rendering innocuous the products 
of Bacillus tetani, the quantity required for neutralising the toxin is 
considerably greater than that used for destroying the toxin of 
diphtheria. 
* Anat. Anzeig., xi. (1895) pp. 156-8. 
t Centralbl. f. Bakteriol. u. Parasitenk., l ta Abt., xviii. (1895) pp. 257-64. 
1895 3 A 
