THEORY OF FERMENTATION 379 



and exactly as they stipulate that such experiments should 

 be conducted with the one sole difference, indispensable to 

 the correctness of our observations, that we carefully 

 guarded ourselves against those causes of error which they 

 did not take the least trouble to avoid. It is possible to 

 produce a ready entrance and escape of pure air in the case 

 of the double-necked flasks which we have so often em- 

 ployed in the course of this work, without having recourse 

 to the continuous passage of a current of air. Having made 

 a file-mark on the thin curved neck at a distance of two or 

 three centimetres (an inch) from the flask, we must cut 

 round the neck at this point with a glazier's diamond, and 

 then remove it, taking care to cover the opening im- 

 mediately with a sheet of paper which has been passed 

 through the flame, and which we must fasten with a thread 

 round the part of the neck still left In this manner we 

 may increase or prolong the fructification of fungoid 

 growths, or the life of the aerobian ferments in our 

 flasks. 



What we have said of penicillium glaucum will apply 

 equally to mycoderma cerevisiae. Notwithstanding that 

 Turpin and Trecul may assert to the contrary, yeast, in 

 contact with air as it was under the conditions of the 

 experiment just described, will not yield mycoderma 

 vini or mycoderma cerevisiae any more than it will pent- 

 cillium. 



The experiments described in the preceding paragraphs 

 on the increase of organized ferments in mineral media of 

 the composition described, are of the greatest physiological 

 interest. Amongst other results, they show that all the 

 proteic matter of ferments may be produced by the vital 

 activity of the cells, which, apart altogether from the in- 

 fluence of light or free oxygen (unless indeed, we are deal- 

 ing with aerobian moulds which require free oxygen), have 

 the power of developing a chemical activity between carbo- 

 hydrates, ammoniacal salts, phosphates, and sulphates of 

 potassium and magnesium. It may be admitted with truth 

 that a similar effect obtains in the case of the higher plants, 

 so that in the existing state of science we fail to conceive 

 what serious reason can be urged against our considering 



