298 THE MICROSCOPE. 



worked at a higher temperature than brewers' wort, fer- 

 tnentation commences earlier, and the yeast-cell grows to a 

 much larger size. It is, indeed, forced in this way much 

 as a plant in a hothouse is, and then obtains to greater 

 perfection in a shorter time. It will, however, be seen 

 that it sooner becomes exhausted ; and now, if we take a 

 portion of this yeast and add it to barley Avort, and at the 

 same time keep it in a temperature of from 60"^ to (^5°. 

 Fahr., it ferments languidly, and small yeast-cells are the 

 product. If the yeast is allowed to stand in a warm 

 place for a few days, it partially recovers its activity, but 

 never quite. AVith such a yeast there is always a good 

 deal of torulse mixed up with the degenerated cells, and 

 sometimes a filamentous mass, which falls to the bottom of 

 the vessel ; from this stage it readily passes to that of 

 must and mildew, and then becomes a wasteful feeder or 

 destroyer. 



With yeast already in a state of exhaustion, we have 

 seen a crop of fungus produced in the head of a strumous 

 bo}^, seven years of age, who was much out of health, and 

 had suffered from eczema of the eyelids, with impetigo. 

 On placing portions of the broken hairs on a glass slip, 

 and moistening with a drop of liquor potassa3, spores and 

 torulas were seen in abundance ; represented in Plate I. 

 No. 14. 



In another experiment Ave took portions of penicillium 

 and aspergillus moulds, and added these to sweetwort, 

 and stood them by in a Avarm room. On the second 

 <iay afterAvards in one of the solutions, and the third in 

 the other, fermentation had fairly set in ; the surface of 

 the solution Avas covered with a film, Avhich proved to be 

 Avell-developed ovoid spores, filled Avith smaller granular 

 spores [conidia) : Plate I. i^o. 8. On the sixth day the 

 cells changed in form and Avere more spherical. Again 

 removing these to another supply of fresh Avort, the results 

 obtained Avere quite characteristic of exhausted yeast 

 ferment. 



Extreme simplicity of structure characterises all moulds 

 or mildcAvs. Their reproductive organs are someAvhat 

 more complex, and both in penicillium and aspergillus the 

 mycelium terminates in a club-shaped head, bearing upon 



