120 Transactions of the Society. 



grown under the two conditions. They might be taken for dif- 

 ferent species, and no mere microscopic examination would suffice 

 to show what they were. 



Speaking of the pecuHar effects of yeast and other ferments, he 

 observes that " there is only a slight relation between the weight of 

 the yeast formed and the weight of sugar decomposed; with all 

 other known beings the weight of the nutritive matter assimilated 

 is of the same order of quantity as the weight of the aliments 

 brought into play. The discrepancy where it exists is relatively 

 slight. Such is not the life of yeast. For a weight a of yeast 

 formed, the weight of the sugar decomposed is 10 a, 20 a, 100 a, 

 and even more." 



The growth and generation of ferments in mineral media are 

 regarded by M. Pasteur as having " a great physiological interest." 

 He says, " They demonstrate, among other results, that all the pro- 

 tein matter of yeasts may have their origin in the vital activity of 

 cells putting in action hydrocarbonous substances without the 

 influence of light or free oxygen — or with free oxygen in the case 

 of the aerobics — together with salts of ammonia, phosphates, and 

 sulphates of potash and magnesia. It might even with rigour be 

 admitted that a similar effect is produced in the higher plants. 

 What serious reason can be invoked in the present state of science 

 for not considering this effect as general ? It would not be illogical 

 to extend the results we speak of to all plants, and to believe that 

 the protein matters of plants, and perhaps even of animals, are 

 formed exclusively by the activity of cells acting on the ammoniacal 

 salts and the mineral salts of the sap, or of the plasma of the blood 

 and the hydrocarbonous matters, of which the formation in the 

 higher plants only requires the aid of the chemical forces of green 

 light. 



" According to this view the formation of protein substances is 

 independent of the great act of reduction of carbonic acid under 

 the influence of light. ... As in plant production by a hydro- 

 carbonous matter in a mineral mediiun, the hydrocarbonous matter 

 may vary greatly, and we comprehend with difficulty how it 

 reduces itself to its elements before serving for the composition of 

 the protein matters, we may hope to obtain as many distinct 

 protein bodies, and even celluloses, as there are hydrocarbonous 

 matters." M. Pasteur states that he is engaged in experiments of 

 this description. He further remarks that if solar radiation is 

 indispensable for the decomposition and formation of the proximate 

 principles of the larger plants, certain lower ones can do without it, 

 and still form a variety of the most complex substances, so that 

 life in inferior forms might exist even if sunlight disappeared. 



Objections have been made to M. Pasteur's theory of the action 

 of ferments by various authorities, and the controversy is still going 



