ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 379 



Simple and Rapid Method of Preparing Agar and Gelatin 

 Media.* — Bisserie describes a simple method for making quite clear 

 culture media. 



The agar, gelatin, or any other medium is melted up in a water bath 

 in a beaker A (fig. 67). When the medium is liquefied an inverted 

 flask B is placed on the bottom. The mouth of the flask has been 

 previously covered in the following manner. First, a layer of cambric 

 (batiste) is tied on ; over this is applied a disk of filter paper (chardin), 

 and the latter covered and kept in place by means of another piece of 

 cambric. The whole apparatus is then placed in an autoclave, which is 

 heated at 100° (valve open) until all the air is driven out, then with the 

 valve closed at 120°. By this means all the air in B is driven out and 

 replaced by steam. After a few minutes at 120"' the autoclave is 

 allowed to cool. When the indicator points to 

 zero the valve is opened very slowly, in order 

 to let in air very gradually. In consequence of 

 the cooling the atmospheric pressure drives all 

 the hot liquid from A into B, and thus within 

 half-an-hour may be obtained a perfectly clear 

 and sterile medium. 



(2) Preparing: Objects. 



Observations on Bacterial Capsules.t — A. 



Hamm advocates the use of Weidenreich's method ^^- ^ 



of fixation by osmic acid vapour for the examina- Pig. 67. 



tiou of bacterial capsules. The author employs 



a tube in which the fixation may be carried out, which he considers to 

 have advantages over the modified Petri dish devised by E. Levy. 

 This tube is wide-mouthed and bulb-ended, and closed by a ground- 

 glass stopper ; the bulb is filled with glass-wool, which, after sterilisa- 

 tion, is impregnated with 1 p.c. osmic solution or 1 p.c. chromic acid. 

 Cleaned slides are placed in the tube for 1-2 minutes, then taken out 

 and filmed and replaced in the tube for 20-40 seconds, dried in the air 

 and stained either by Klett's method or by Giemsa. 



To demonstrate the capsules of bacteria from artificial media the 

 films should not be made with water, but with some viscid fluid, such as 

 blood serum or ascitic fluid. 



The author considers that the capsule and the intracapsular network 

 result from the production of slime by the organism. The capsule 

 appears larger in young bacilli and diminishes with age. The substance 

 of the capsule consists of nucleo-proteid and contains no mucin. 



Studying the Heart of Arca.| — A. Theiler first benumbed the 

 animals either in 2 p.c. solution of cocain in sea-water, or 5 p.c. alcohol 

 in order to prevent contraction. After 5 or 6 hours they were transferred 

 to the fixative (sublimate with 5 p.c. acetic acid), by which the shell was 

 at the same time dissolved. 



* Ann. Inst. Pasteur, xxi. (1907) pp. 235-6 (1 fig.). 



t Ceutralbl. Bakt., Ite Abt. Orig., xliii. (1907) p. 287. 

 X Jen. Zeitschr. Natur., xlii. (1906) pp. 115-12. 



2 C 2 



