128 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
rotating grinding apparatus it is then given the spherical surface of 
determined radius, using emery of gradually increasing fineness. Then 
follows the polishing. To determine whether the lens has the correct 
form it is fitted in or on a normal concave or convex form of glass or 
rock-crystal, when any difference of surface is recognised by the pro- 
duction of Newton’s rings. 
)S. Technique.* * * § 
(1) Collecting- Objects, including: Culture Processes. 
Improvement in the Plate-Cultivation Method.f — Dr. Pfaffenholz 
recommends a platinum brush for smearing sputum, diphtheritic mem- 
brane, &c., on agar or gelatin plates. An important requirement of the 
stroke-method is a sufficiently firm consistence of the agar ; this may be 
attained bv adding the agar to the bouillon after the latter has been 
neutralised with soda. 
Demonstrating the Presence of Bacillus coli communis in Water.J 
— Dr. Th. Smith has for four years used the following method for 
detecting the presence of B. coli communis in water. A series, usually 
ten, of fermentation flasks is provided with 1 per cent, dextrose-bouillon 
and 0*1-1 ccm. of the water added. If, after three or four days, one or 
more of the flasks be found to contain 40-60 per cent, of gas in the 
closed tube, if the reaction be strongly acid, if the increase of the bacilli 
be slight and quite ended by the fourth day, the presence of B. coli 
may be regarded as certain. Such tubes almost always contain pure 
cultivations, as plate-cultures of the sediment will show. The isolation 
must, however, be made within the week, for the acid formed from the 
sugar soon kills the culture. If the water be very impure, it must be 
freely diluted on account of the great number of fermenting bacteria 
present ; among these are Proteus and B. cloacae , whose gas reaction is 
easily distinguished from that of B coli. Ladis aerogenes offers greater 
difficulties. 
Method for Hermetically Sealing Cultures of Bacteria. § — Dr. C. F. 
Dawson seals cultures as follows. The end of the tube is flamed and 
trimmed down level with the mouth of the tube, on which is then placed 
a cover- glass of the same size as the mouth. A piece of sheet gelatin 
is next stretched over the mouth of the tube and temporarily fixed with 
a rubber band. After the gelatin has set, for of course it is applied 
warm, the band and edge of the gelatin are trimmed off close under the 
flange. The gelatin cover, which will be quite dry in about half an hour, 
is coated with shellac varnish made from the following formula : — 
Absolute alcohol 100 parts ; white shellac 45 parts ; balsam of copaiba 
4 parts. Allow to stand for a fortnight and use the supernatant fluid. 
* This subdivision contains (1) Collecting Objects, including Culture Pro- 
cesses; (2) Preparing Objects ; (8) Cutting, including Imbedding and Microtomes; 
(1) Staining and Injecting ; (5; Mounting, including slides, preservative fluids, &c. ; 
(6) Miscellaneous. 
t Hygien. Rundschau, 1895, No. 16. See Centralbl. f. Bakteriul. u. Parasiteuk.,' 
l te Abt., xviii. (1895) p. 467. 
X Centralbl. f. Bakteriol. u. Parasitenk., l te Abt., xviii. (1895) pp. 494-5. 
§ Amer. Mon. Micr. Journ., xvi. (1S95) pp. 822-4. 
