298 THE MICROSCOPE. 



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

 mentation 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 wort, and at the 

 same time keep it in a temperature of from 60 to 65 

 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. With 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 

 boy, 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 potassa?, spores and 

 torulae were seen in abundance ; represented in Plate I. 

 No. 14. 



In another experiment we took portions of penicillium 

 and aspergillus moulds, and added these to sweetwort, 

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

 day afterwards in one of the solutions, and the third in 

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

 the solution was covered with a film, which proved to be 

 well-developed ovoid spores, filled with smaller granular 

 spores (conidia) : Plate I. No. 8. On the sixth day the 

 cells changed in form and were more spherical. Again 

 removing these to another supply of fresh wort, the results 

 obtained were quite characteristic of exhausted yeast 

 ferment. 



Extreme simplicity of structure characterises all mould* 

 or mildews. Their reproductive organs are somewhat 

 more complex, and both in penicillium and aspergillus the 

 mycelium terminates in a club-shaped head, bearing upon 



