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allowing it to stand for 24 hours at 25° C, and then infecting a 
fresh tube from it, which was also kept for 24 hours at 25° C. 
Saccharomyces cerevisiae Hans. and S. anomalus Hans. were the 
species used. 
The first set of experiments consisted in testing the effect 
of the porosity of the block upon which the spore-culture is 
made, it being suggested by Klebs that the function of the 
Plaster of Paris block was to serve as a means to separate the 
food materials from the cells. Obviously, then, the more porous 
the material the better separation there would be. 
The substances used were Plaster of Paris, a pad of filter 
paper, porous porcelain of two kinds, cardboard, and pieces of 
a plant pot. These are arranged in the order of their porosities, 
the first two being equaily porous. These were placed in 
separate covered glass dishes, and were moistened with a few 
drops of distilled water after the beer-wort had been soaked up. 
The vegetation on them was examined after 48 hours in the 
series, where S. cerevisiae was the species used ; and it was found 
that the number of spores produced varied according to the 
porosity of the material. Arranging the materials in the order 
of the number of spores formed thereon, the arrangement 
corresponds exactly to that given above as representing the 
porosities of the materials. 
A similar experiment was made, using S. anomal/us Hans. in 
the place of S. cerevisiae. The vegetation in this case was ex- 
amined after 72 hours, a longer time being required for the 
formation of spores in this species. The results here corre- 
sponded exactly to those in the preceding case. 
At first sight these results seem to support Klebs’ view, but it 
must be borne in mind that not only does better porosity imply 
better separation of food material, but also better eration. In 
the case of a poorly porous substratum, the cells are immersed in 
comparatively large drops of liquid, while a very porous sub- 
stratum leaves the cells practically exposed to the air, being 
kept moist by the large amount of aqueous vapour rather than 
a film of liquid. 
An attempt was then made to estimate the effects of the 
presence or absence of nutrient substances. Five sets of spore: 
cultures were made :— 
a. In which the blocks were kept moist with fresh beer 
wort. 
6. In which the blocks were kept moist with a mixture of 
' 25 per.cent. fresh beer-wort and 75 per cent. distilled 
water. 
c. In which the blocks were kept moist with a mixture of 
10 per cent. beer-wort and 90 per cent. distilled water. 
