SYSTEMATICALLY SELECTED YEASTS. 



33 



to the mouth of the former. The bent tube passing from 

 the top of the vessel is made in two pieces, which are 

 joined at c with india-rubber tubing. The end d of the 

 tube is closed by a plug of cotton-wool, tightly packed 

 in a glass capsule ; at e there is the enlargement in the 

 tube mentioned above, to ensure against infection occur- 

 ring, especially shortly after sterilisation. In place of the 

 cotton-wool filter we now generally employ asbestos ; this 

 is contained in a brass cylinder which is screwed tightly 

 on to the tube, and is provided with a loosely fitting cover 

 (Fig. 6). 



In the form shown in Fig. 

 5, the bent tube is fixed to 

 the can. It may, however, 

 also be fastened by means of 

 a screw union as suggested 

 by my assistant, Mr. Poulsen ; 

 this is shown in Fig. 6, whilst 

 Fig. 7 shows the screw union 

 in detail. The diameter of 

 the cone of the union (shown " 

 by the dotted line) is 28 mm. 

 at the larger, and 25 mm. at 

 the smaller end ; its length is 

 1 8 mm. ; it must, of course, 

 be well ground in. This 

 arrangement admits of the whole tube being detached when 

 the vessel requires cleaning, and there is, therefore, no need 

 for the rubber connecting tube (Fig. 5, c). The cleaning is, 

 however, readily effected in both cases ; if the union is well 

 made this form is to be preferred. The chief point in con- 

 nection with these and similar vessels is that they must 

 be perfectly tight so tJtat air can only enter through tJie bent 

 tube. 



The nutrient solution employed is ordinary hopped wort 



D 



FIG. 5. 



