of the Fishery Board for Scotland. 



473 



was also titrated against a carefully prepared standard hydrochloric acid 

 solution. 



Micro-Organisms in the Air. 



The method followed was that of slowly aspirating a small volume of 

 air through a liquid nutritive medium, which was subsequently solidified 

 and incubated at a temperature between 15° and 16° C. 



The nutritive solution was Koch's peptonised broth sterilised under 

 pressure at 120° C, and rendered alkaline both to litmus and yellow 

 turmeric paper, because of the amphoterie or double reaction of animal 

 fluids. The bulb tubes (see figure), contrived by Miguel of Paris, and 

 used by him at the Montsouris Observatory for bacteriological examina- 

 tion of air, were used. 



These were prepared as follows : — Rinsed with strong sulphuric acid 

 and washed first with distilled water till 

 washings were neutral, and then with A 

 alcohol ; a plug of sterilised cotton wool 

 in the end A and a cap of the same put 

 over the pointed end B, and lastly, kept w 

 for an hour in the hot chamber at 150° C. 

 One dozen such tubes were each charged 1 

 with 10 cc. of the broth on 4th Sept., 1 

 sterilised at 100° C, and fastened in the I 

 laboratory in such a way as to prevent 

 the rolling of the ship affecting the level I 

 of the fluid in them. On the 19th y^^-W. 

 Sept. all the tubes were sterile but one, /at- 1» 



which showed turbidity during the first I^^^^S 

 week. One dozen sterilised test tubes ^BCi^T^^^^ 3 ^ ^ 



were each charged with 10 cc. of a ifl II 



sterilised 15 per cent, solution of gelatine, ft m 



and finally kept for half an hour at 100° ^=#^ 

 C. for two successive days. 



The experiments were made on the forecastle deck, when the ship was 

 in motion, and facing the direction of the wind. The tube was fixed to a 

 support on the deck, the plug at A removed, and the aspirator connected. 

 The cap at B was now removed, this end of the tube heated by the flame 

 of a spirit-lamp, and allowed to cool, and then the amount of air slowly 

 sucked through. This done, the end at B was again heated, and the cap 

 replaced, as was also the plug at A. The contents of the tube were, with 

 the usual precautions, transferred to one of the tubes of gelatine (previously 

 liquefied), thoroughly mixed, plugged, and capped, and allowed to solidify, 

 and incubated for 4 weeks. 



