ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
593 
of the electrical organs, usually only seen with great difficulty, were ren- 
dered perfectly clear by Golgi’s method. The preparations were stained 
in chrom-osmic acid (4 : 1), and, after 3—4 days, were washed in dilute 
silver nitrate solution, and then immersed for 1-3 days in 0*75 silver 
nitrate. 
Concentration of Therapeutic Sera by Freezing.* — Prof. 0. Bujwid 
has been able to obtain strongly concentrated diphtheria and tetanus 
sera by means of freezing. The ice is devoid of antitoxins ; these, to- 
gether with other constituents of the sera, remaining in solution. On 
freezing a bottle containing serum, the latter separates into ice crystals 
and a small quantity of brownish fluid. After thawing at room tempera- 
ture, the contents of the bottle are found to have separated into two 
layers; the upper, which is quite colourless, contains only a small 
quantity of solid matter, and is practically water. Its antitoxic action 
is almost nil. The lower layer is of a yellow colour, perfectly clear, 
and contains all the antitoxins. After freezing two or three times, a 
serum is obtained which is 2J to 3 times more concentrated than the 
original, so that 1-2 ccm. contain 1000 antitoxin units. 
Pastes and Cements for General Purposes.! — (1) Gum arabic, 
4 parts ; starch, 3 parts ; sugar, 1 part. Dissolve the gum in water 
sufficient to take up the starch, add the sugar, and heat the whole on a 
water-bath until the starch is completely dissolved. 
(2) Collodine is a paste made by treating starch with water rendered 
strongly alkaline. 
(3) Triticine is a paste made by dissolving equal parts of dextrine 
and starch in water and then heating. A little glycerin is added to 
make the paste pliable and elastic when dry, and a little boric acid or 
thymol to prevent fermentation. 
(4) Gum arabic, 70 parts; water, 200 parts; aluminium sulphate, 
2 parts. Dissolve the aluminium sulphate in some of the water, the 
gum in the rest, and mix the two. 
(5) Gelatin, or best glue, 2 parts; water, 6 parts. Soak the gelatin 
in the water until it is soft throughout, then melt in a water-bath. Add 
1-2 parts of chloral hydrate, and continue to heat gently for some time. 
(6) Cover 100 parts of gelatin with water, and let stand until the 
gelatin is saturated. Then melt in water-bath and add 150 parts 
alcohol, 500 parts water, 50 parts glycerin, and 20 parts carbolic acid. 
This makes a very powerful cement. 
Bronzing of Copper .} — For bronzing copper, Herr Mondil gives the 
following procedure : — After the surface has been thoroughly cleaned, it 
is brushed over with a mixture composed of 20 parts by weight of castor 
oil, 80 parts alcohol, 40 parts soft soap, and 40 parts water. The mor- 
dant is left on the metal until it is sufficiently stained. The surface is 
then dried with hot saw-dust, and afterwards covered with a thin layer of 
varnish. 
* Centralbl. Bakt. u. Par., l te Abt., xxii. (1897) pp. 287-8. 
t Amer. Mon. Micr. Journ., xviii. (1897) pp. 296-8. 
+ Centralztg. f. Opt.u. Mech., 1897, p. 4. See Zeitschr. f. angew. Mikr., iii. (1897) 
p. 118. 
