492 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
Selenium as a Mounting Medium for Diatoms.* * * § — Selenium, says 
Herr G. Marpmann, is an element of a brown colour, of sulphur-like 
consistence, with a refractive index nearly as great as that of sulphur, 
and when heated melts to a brownish-red fluid. By itself alone, selenium 
is too dark for a mounting medium, but by mixing with sulphur or arsenic 
this disadvantage is obviated. By mixing equal parts of sulfur depu- 
ratum and selenium metallicum , rubbing them together and melting in a 
test-tube, a red fluid is obtained, and this on cooling becomes a bright 
yellowish-red, and maintains its transparency for a considerable time. 
It seems that when mounted the preparations are cloudy or even opaque 
in places, and in order to remove these defects it is advisable to place 
the mounted preparations in a thermostat at 150°. 
Of selenium compounds, selenium ethyl Se (C 2 H 5 )^. is a fluid which 
possesses a boiling point between 107° and 108°. In this fluid con- 
siderable quantities of sulphur and selenium can be dissolved. In this 
way is produced a thick oily fluid, having a refractive index of about 
1*90, and forming a medium which should meet the requirements of 
diatomists. 
Picro-formalin in Cytological Technique.! — Mr. Graf states that 
the best fixative for demonstrating the cell* structure of the lower animals 
is picro-formol in varying strengths, 1 vol. saturated aqueous solution of 
picric acid and 1 vol. of 5, 10, or 15 per cent, formol, or 95 vols. picric 
acid solution and 5 vols. formol, or 90 vols. picric acid solution and 10 
vols. formol. The animals (Clepsine nepheloidea sp. n. Whitm.) are 
placed (alive) in the mixture for 30 minutes. After immersion in alco- 
hol of increasing strength up to absolute, they are imbedded in paraffin. 
Sections 3 /x thick were stained with haematoxylin and Bordeaux-red. 
By this procedure the delicacies of the cell structure, network, microsomes, 
and vacuoles, are rendered extremely clear. 
Preservative for ; Freshwater Sponge.!— Mr. F. L. Washburn finds 
the following solution to be of value for preserving freshwater sponges. 
Pure glycerin 2/3 ; 3 per cent, formalin 1/3. In this the green sponge 
will keep for at least three months, the liquid remaining perfectly clear, 
and allowing the external anatomy of the sponge to be beautifully 
seen. 
(6) Miscellaneous. 
Microbiological and Serotherapeutical Technique^ — M. A. Bes- 
son’s guide to laboratory work, dealing with the]technique of microbiology 
and serum therapeutics, is one that deserves to obtain universal approba- 
tion. It is divided into a general and special portion, the first describing 
the various methods in use at laboratories,^ the second describing the 
numerous species of pathogenic organisms. In a third section the 
bacteriological examination of water and air is treated of. 
* Zeitschr. f. angew. Mikr., iv. (1898) pp. 6-8. 
t State Hospitals Bull., 1897, No. 1 ; also Neurol. Centralbl., xvi. (1897) p. 550. 
See Zeitschr. f. wiss. Mikr., xiv. (1898) p. 469. 
X Journ. Applied Microscopy, i. (1898) p. 73. 
§ Paris, 1898, 223 figs. See Zeitschr. f. wiss. Mikr., xiv. (1898) pp. 519-20. 
