TRANSACTIONS OF SECTION K. 793 



the rays of a certain region of the spectrum. While all these views have been 

 advanced, however, there is little positive information hearing upon either the 

 formation or the function of the pigment. 



Very little progress has been made with the problem of the construction of 

 proteid matter in the plant, which still confronts us. The question of its relation 

 to the mechanism of photosynthesis has received some attention without leading 

 to any satisfactory conclusion. Winogradski's success in cultivating the nitrate 

 bacteria upon purely inorganic matter reveals an unexpected constructive power 

 in some forms of vegetable protoplasm. The question of the energy made use of 

 in proteid construction is in an equally unsatisfactory condition. Laurent, 

 Marchal, and Oarpiaux have stated that the rays of the violet and ultra-violet 

 region of the spectrum are absorbed and devoted principally to the construction 

 of nitrogen compounds from the nitrates, or the compounds of ammonia, which are 

 absorbed by the plant, while the intervention of the chlorophyll apparatus is 

 unnecessary for this purpose. The experiments which they give in considerable 

 detail upon this absorption carry much weight and appear conclusive. Unfortu- 

 nately other observers have failed to confirm them, so that at present the matter 

 must be left open. 



Among the problems connected with the nutrition of the plant, the part 

 played by alcohol has recently come into prominence. Alcohol was originally 

 associated only with the lower fungi, and especially with the yeast plant. Bio- 

 logical problems of grave importance arose in connection with the Saccharomyces, 

 apart from what seemed at first the larger question, viz., the nature of fermentation. 

 A prolonged study of the latter phenomenon led Pasteur to the view that 

 alcoholic fermentation is only the expression of the partial asphyxiation of the 

 yeast, and its efforts to obtain oxygen by the decomposition of the sugar. 

 It is hardly necessary here to remind you of the controversies that centred 

 about the question of fermentation and the theories held and abandoned as to its 

 cause. The biological phenomena have, however, a claim now upon our attention 

 in the light of some very remarkable researches that are calling for our attention 

 and criticism to-day. Pasteur's explanation of the behaviour of the yeast was, as 

 •we have seen, such as to connect it with the respiration of the plant. When 

 oxygen was withheld from active yeast 60-80 parts of sugar disappeared for one 

 part of yeast formed. When oxygen was present not more than ten parts of sugar 

 were decomposed for the same amount of yeast production. Undoubtedly the 

 stimulus of asphyxiation materially stimulated the yeast metabolism. 



But certain observations did not agree with Pasteur's explanation. An 

 energetic fermentation takes place in the presence of oxygen, the plant multiplies 

 extremely quickly, and its metabolism appears very active. Schiitzenberger argued 

 against Pasteur's explanation with some force, emphasising these points of disagree- 

 ment between his hypothesis and the facts, and claimed that the matter rather 

 concerned nutrition than respiration. He based his view on experiments carried 

 out to ascertain how respiration was affected under changed conditions. 



The results he obtained were briefly the following : — 



(1) In a watery liquid without sugar, but containing oxygen in solution, the 

 quantity of oxygen absorbed in unit time by a gramme of yeast is constant, 

 whatever proportion of oxygen is present. 



(2) In a saccharine liquid containing albuminous matter as well as sugar, and 

 with oxygen in solution, the same result is obtained, except that the quantity 

 absorbed in unit time is greater. 



(3) In two digestions carried on side by side for some time, one being supplied 

 continuously with oxygen and the other deprived of it, the former produced most 

 alcohol. 



If the decomposition of the sugar had been the result of the respiratory activity 

 of the yeast cells at the expense of the combined oxygen of the sugar, it would 

 seem that fermentation should either not have taken place at all in the presence of 

 free oxygen, or that it should have been much less than in the other case, whereas 

 the reverse is what is found. Hence Schiitzenberger advocated the view that the 

 sugar is alimentary and not respiratory. 



