APPENDIX. 399 



thermostats with regulator should be obtained, or, failing this, one of the 

 small egg-hatching machines, of which there are several in the market, may 

 be used. 



STERILIZED VESSELS FOR THE RECEPTION OF VARIOUS MEDIA. 



Ordinary test tubes, flasks, and other special glass apparatus, are first 

 carefully washed with soap and water, then with boiling solution of per- 

 manganate of potash, to which a few crystals of oxalic acid are added. 

 They are then rinsed with distilled water, and are allowed to drain on a 

 rack for some time, after which they are carefully plugged with cotton wool, 

 care being taken that the wadding inside the neck is perfectly smooth and 

 firm, the tuft outside being large enough to overlap well the lip of the test 

 tube. These plugs in situ may be covered with paper, which keeps off 

 the dust. They are heated for an hour in the hot air chamber at 150 

 C. For the reception of fluid media, Salomonsen recommends the use of 

 a small flask or test tube of which the neck or upper part is so drawn 

 out that it has a comparatively narrow mouth. The mouth is closed by 

 a piece of indiarubber tube a couple of inches long. The tube is washed 

 with bichloride of mercury solution, then with distilled water, is wrapped 

 in hard parchment paper and sterilized at 100 C. in the steam sterilizer. 

 It is then filled for half its length with cotton wadding that has been 

 sterilized at 150 C. in the hot air chamber. The flasks are sterilized as 

 above. For these stoppers the following advantages are claimed : (i) In 

 opening and closing the flasks, the wadding and dust that is collected on 

 it are not touched. (2) The apparatus is opened and closed at a point 

 which can always be easily kept free from dust. (3) The opening through 

 which the inoculation is made is smaller than in the case of the ordinary 

 test tubes. Chamberland has devised flasks and test tubes which differ 

 from these only in having glass in place of indiarubber caps. 



PREPARATION OF FLUID CULTURE MEDIA. 

 Beef Broth Bouillon. 



To prepare beef extract for the nutrition of micro-organisms, take a 

 pound of lean beef, mince it fine ; add to this a litre of pure water, mix 

 thoroughly, and allow to stand in a cool place for twenty-four hours ; again 

 mix thoroughly and squeeze through a cloth, passing sufficient additional 

 water through the meat to again make up the quantity of fluid to a litre ; 

 boil the extract thus obtained for half an hour, render it neutral, or very 

 slightly alkaline, by adding a saturated solution of mixed sodium hydrate, 

 sodium carbonate, and sodium phosphate ; with a bit of gummed paper 

 fasten a strip of neutral litmus paper and one of turmeric paper to the end 

 of a glass rod ; as soon as the faintest alkaline reaction is obtained, add no 

 more of the alkaline solution ; boil for an hour ; allow to cool, and remove 

 the fat ; again filter into a large stock flask or into test tubes that have been 

 plugged with cotton wadding and sterilized as above. These vessels, with 

 their contents, should now be boiled in a potato steamer or other steam 

 sterilizing apparatus for a quarter of an hour on each of two or even three 

 successive days, the wadding plugs being protected from dust by several 

 layers of paper tied over them, or by means of thin indiarubber caps that 

 have been washed in a solution of corrosive sublimate. The meat extract 

 may be modified by the addition of various materials, such as .5 per cent. 



