344 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
Medium for Bacteriological Examination of Water. * * * § — Herren 
W. Hesse and Niedner give the following as the most suitable medium 
for water examination: — agar 1*25 per cent.; albumose (Herdgen) 
0*75 per cent.; distilled water 98 per cent. This medium does not 
require correction for acid or alkali. 
Protogen as Culture Medium, f — Herr J. Laboschin recommends 
protogen, on the grounds that most bacteria do better on it than on 
other albuminous media, and that it is more easily manipulated. The 
author at first made his own medium by beating up the whites of eggs 
with twice their bulk of water. Afterwards he used the Hochster 
protogen. Of the latter, 10 grm. were mixed with 3 grm. salt and 
1000 ccm. of meat water. This produced a clear transparent medium. 
(2) PreparingiJObj ects. 
• 
Collecting and Preserving Diatoms. — The following hints on this 
subject are given by Dr. R. Lauterborn.J Among fixing reagents, 
Flemming’s chromo-aceto-osmic acid, and sublimate in either water or 
alcohol solutions, demonstrate the most delicate structural features of 
the nucleus and cytoplasm during division. Piero- sulphuric acid, 
followed by a haematoxylin stain, gives excellent pictures of the chro- 
matic elements of the nucleus. A 1 per cent, osmic acid solution serves, 
in unstained preparations, to bring out the arrangement of the cytoplasm, 
the chromatophores, and other inclusions of the cell. A 45 per cent, 
solution of iodic alcohol is recommended for the study of the so-called 
“ red granules ” of Biitschli. After remaining about 15 minutes in the 
fixing solution, the diatoms were passed, before staining, through alcohols 
of increasing strength up to absolute, and then through alcohols of de- 
creasing strength to distilled water. The most useful stain is a weak 
solution of Delafield’s haematoxylin ; safranin is useful in demonstrating 
the centrosome and nucleoles. When stained, the specimens were 
passed successively through 35, 70, 95 per cent., and absolute alcohol 
into oil of cloves. It is possible to stain the diatoms to a certain extent 
during life in a very weak solution of methylen-blue (1 in 100,000), in 
which they live for days. For magnification, a Seibert apochromatic 
objective of 2 mm. focal length was usually employed, in combination 
with a No. 12 ocular, giving a magnification of about 1200. 
Methods for Demonstrating Structure of Protoplasm.§ — In his 
paper on the structure of the protoplasm of human epidermal cells, 
Dr. Karl Herxheimer devotes a special section to technique. He har- 
dened fragments of skin in 10 per cent, formol solution for 48 hours, 
washed in water, placed in 70 per cent, alcohol for 24 hours, and in 
absolute for the same time. They were then soaked in a mixture of 
alcohol and ether for 2*3 hours, imbedded in celloidin, and sectioned. 
Various stains were tried, of which the most novel was a basic anilin 
pigment — “ cresylechtviolett,” which was employed in concentrated 
* Zeitscbr. Hygiene, xxix. (1892) No. 3. See Centralbl. Bakt. u. Par., l te Abt., 
xxv. (1899) p. 392. 
t Inaug. Diss. Freiburg, 1898, 34 pp. See Centralbl. Bakt. u. Par., l te Abt., 
xxv. (1899) p. 391. J F. B. Kowley in ‘ Natural Science,’ xiii. (1898) pp. 415-6. 
§ Arcli. f. Mikr. Anat., liii. (1899) pp. 510-46 (1 pi.). 
