ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



261 



2-i grra. dry pyrogallic acid. The bell-jar is then applied so that the 



end of the long tube dips into the Petri dish. Both stop-cocks are now 



opened, and hydrogen or coal-gas introduced through the short upper 



tube. When the apparatus is full both taps are turned and an air pump 



applied to the short tube. After opening the stop-cock, one or two 



strokes of the piston produce a sufficient vacuum, and then the tap is 



closed again. By means of a 



piece of rubber tubing applied Fig. 63. 



to the long tube, strong potash 



solution is introduced (109 grm. 



solid KHO in 145 ccm. water) 



into the Petri's dish. It is 



necessary to make the potash 



solution some time before using. 



The whole operation of putting 



the apparatus into complete 



working order does not occupy 



five minutes. The apparatus 



has been used with great success 



for tetanus, malignant oedema, 



rauschbrand, and B. aerogenes 



capsulatus. 



(2) Preparing Objects. 



Preparation of Plague Vac- 

 cine. * — Prof. A. Lustig and 

 Prof. G. Galeotti have extracted 

 from plague bacilli a poison- 

 ous nucleo-proteid, which is 



capable of conferring immunity even in small doses, by the following 

 method : — " We cultivate the plague bacilli in large glass dishes con- 

 taining a stratum of common agar-agar. After some days' develop- 

 ment we scrape with a bone spatula the colonies which have formed, 

 and dissolve the mass in a 1 per cent, solution of caustic potash. We 

 then add a very dilute solution of either hydrochloric or acetic acid 

 until a slight acid reaction is introduced, and we collect in a filter the 

 precipitate formed. After careful washing, the precipitate itself is dried 

 in vacuo, and in the presence of sulphuric acid, or else immediately re- 

 dissolved in a 0*5 per cent, solution of carbonate of soda. The dried 

 substance, which has lost none of its chemical and biological properties, 

 is easily redissolved in a solution of carbonate of soda when required. 

 The solution of this substance may also be passed through a Chamber- 

 land filter for greater guarantee of sterility. The precipitate is com- 

 posed solely of a nucleo-proteid in a state of relative purity. It 

 possesses all the general reactions of nucleo-proteids, is soluble in 

 alkalies, insoluble in dilute acids, gives oti digestion an insoluble pro- 

 duct and a peptone, and on dissociation by sulphuric acid gives nucleinic 

 bases. It is extremely toxic for several animals, and is able to produce 

 the intravascular coagulation of the blood." 



Brit. Med. Jouin., 1900, i. p. 311. 



