ZOOLOGY AND BOTANY, MICROSCOPY, ETC.'' 391 



removed to introduce test-tubes, the temperature falls 10°-15°, but the 

 loss is rapidly recovered, and in 15-20 minutes after the thermometer 

 has risen to 70°, the tubes will have been exposed to a temperature of 

 75° or over, most of the time. 



Nutritive Medium for detecting Sulphide Formers.* — Prof. W. 

 Beijerinck detects sulphide formers by means of white lead. Carbonate 

 of lead is added to ordinary meat-gelatin or meat-agar in quantity suf- 

 ficient to make the plates of a snowy white. The substratum is inocu- 

 lated by pouring over the surface drain- water diluted with distilled 

 water. The plates are incubated at 23° C. In a couple of days the 

 presence of sulphide-forming germs is rendered evident by the appear- 

 ance of brown colonies, the growths of other bacteria being white. As 

 the lead sulphide in the brown colonies is unaffected by air, the re- 

 action is permanent, and is gradually intensified. In order to render the 

 browning more distinct, part of the surface may be covered with a glass 

 plate when the growth has well developed. This not only hinders 

 diffusion, but prevents oxidation of the sulphuretted hydrogen. 



New Covering for Culture-tubes.^ — Dr. W. Hesse recommends the 

 following method for covering the mouth of culture vessels for the pur- 

 pose of preventing evaporation and loss of moisture during prolonged 

 sterilisation and incubation. The cotton-wool plug is covered over 

 with a square piece of coffer dam (sheet rubber used by dentists) the 

 sides of which are about 3 cm. long. Over this is placed another piece 

 of similar size, but having a hole about 2 mm. in diameter punched in 

 the middle. This fastening is so tight that evaporation from the vessel 

 even in the incubator is very slight, and cultures may be kept in the 

 thermostat as long as a month without detriment, provided that the 

 amount of the medium be not too small. 



A similar expedient may be applied to Petri's capsules. 



Substrata for Cultivating Tubercle Bacilli. J — MM. F. Bezancon. 

 and V. Griffon recommend two media for cultivating tubercle bacilli. 

 One of these is a potato disk covered with a thin film of glycerin-agar. 

 The agar fixes the potato firmly in the culture-tube, so that the surface 

 of the potato may be energetically rubbed with tuberculous material. 

 This medium is extremely favourable to growth. The other substratum 

 is made by passing blood from the artery (carotid of rabbit) into tubes 

 containing agar-bouillon. The tubes are then sloped, and when set, a 

 solid surface is obtained on which colonies of tubercle bacilli become 

 evident in 6 days, and in 15 days the growth is extensive. 



New Medium for Cultivating Tubercle Bacillus.§— Herr W. Hesse 

 recommends the following medium for cultivating tubercle bacilli. The 

 pepton is replaced by Heyden's aliment, which is a preparation of 

 soluble albumen with properties intermediate between coagulated albu- 

 men and somatose. The medium is composed of Heyden's aliment 

 5 grm. ; salt 5 grin. ; glycerin 30 grm. ; agar 10 grm. ; normal soda 



* Centralbl. Bakt. u. Par., 2 te Abt., vi. (1900) p. 196. 

 t Op. cit., l te Abt., xxvii. (1900) pp. 258-9. 

 X C.R. Soc. Biol., vi. (1899) pp. 77-9. 



§ Zeitschr. f. Hygiene u. Infektionskr., xxxi. (1899) p. 502. See Zeitschr. f. wiss. 

 Mikroskop., xvi. (1900) pp. 492-3. 



