ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
249 
bands are completely absent. (10) The difficulty of centering the usual 
small type of condenser is avoided. 
For the purely theoretical considerations connected with the system, 
which the author discusses, we must refer the reader to the original 
paper. 
Method of Photographing Large Microscopic Sections.* * * § — Mr. W. 
Forgan uses, for photographing objects having a diameter of over an 
inch, a single landscape lens of about 4^ in. focus. It has a diameter of 
about 1 in., is used with a stop at F 16, and gives excellent definition. 
It is screwed into the front of the camera so that the Microscope is 
altogether dispensed with, the slides being held on a separate carrier- 
board. 
A piece of glass, obscured on both sides, is placed between the 
specimen and the illuminant to diffuse the light. The author strongly 
recommends burning magnesium ribbon as the source of light. 
B. Technique.! 
(1) Collecting- Objects, including Culture Processes. 
Increasing the Toxin Production of the Diphtheria Bacillus. t — 
Dr. Freiherr v. Dungern has found that the addition of human ascitic fluid 
to artificial nutrient media is a good means for increasing the virulence of 
diphtheria bacilli, at least in so far as the production of toxin is con- 
cerned. For making diphtheria antitoxin it is important to be in pos- 
session of a strong toxin. 
Cultivation Medium for Diphtheria Baeillus.§ — Dr. Tochtermann 
recommends the following serum medium for cultivating diphtheria 
bacilli. A 2 per cent, watery solution of agar is treated with 1 per cent, 
pepton, 1/2 per cent, common salt, and 0*3-0 *5 per cent, grape-sugar, 
and the whole filtered. The filtrate is heated from a quarter to half an 
hour with sheep’s blood-serum in equal parts, or of three of serum to 
two of the agar solution. The filtrate is then put into tubes and steri- 
lised in the usual way. 
Improvements in the Technique of the Diphtheria Culture Test. || — 
Dr. A. P. Ohlmacher makes very rapid and successful diagnoses of diph- 
theria by means of the following modifications of the ordinary procedure. 
To the culture medium a decided alkaline reaction is imparted by adding 
to the glucose-beef-pepton-bouillon a saturated solution of sodium hy- 
droxid, drop by drop, until a pronounced blue colour is obtained with 
red litmus paper. The alkalinised bouillon is added to the serum 
before its coagulation. The medium, when rapidly coagulated, forms a 
smooth, moist, slanting surface. This kind of surface, which is a sine 
* Proc. Scottish Micr. Soc., 1894-5, pp. 221-2. 
t This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses; (2) Preparing Objects; (3) Cutting, including Imbedding and Microtomes; 
(4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, &c. ; 
(6) Miscellaneous. 
% Centralbl. f. Bakteriol. u. Parasitenk., l te Abt., xix. (1896) pp. 137-41. 
§ Centralbl. f. Inn. Med., Oct. 5, 1895. See Epit. British Med. Journ., ii. (1895) 
par. 507. 
|1 Medical News, May 4, 1895. 
