1889.] On a pure Fermentation of Mannite and Glycerin. 345 



food is at its maximum. Thus digestion neutralises in a great measure 

 the effects on respiration of any local change of pressure. 



Two persons, both aged twenty-three, were found in the experi- 

 ments related in this paper to require respectively a mean of 

 9*29 and 10*51 litres of air, reduced, to expire 1 gram carbonic 

 acid. Experiments on another person, aged sixty, gave a mean 

 of 11*30 litres of air; and with a number of others the propor- 

 tion of air breathed for a given weight of carbonic acid expired 

 also varied, showing that different individuals breathe different 

 volumes of air to supply their body with the necessary amount 

 of oxygen to make and expire a given weight of carbonic acid. It 

 cannot be doubted that the less the volume of air inspired to burn a 

 certain weight of carbon, the more readily the oxygen taken into the 

 lungs finds its way into the blood, and, therefore, the more perfect the 

 respiratory function. This may have important bearings in medical 

 respects. The age of sixty years apparently necessitated breathing 

 a comparatively large proportion of air (Tl\30 litres) to supply the 

 blood with the oxygen it required. One of the two young men was 

 physically stronger and possessed of a greater muscular development 

 than the other, he breathed 9*29 litres against 10*51 for the other, or 

 took 11*6 per cent, less air into his lungs to yield the necessary oxygen 

 to burn the same weight of carbon within a given time. The corre- 

 sponding difference between the person aged sixty, and the strongest 

 of the two young men amounted to no less than 17'8 per cent. 



X. " On a Pure Fermentation of Mannite and Glycerin." By 

 Percy F. Frankland, Ph.D., B.Sc. (Lond.), Assoc. Roy. 

 Sch. of Mines, Professor of Chemistry in University College, 

 Dundee, and Joseph J. Fox. Communicated by Professor 

 T. E. Thorpe, F.R.S. Received June 17, 1889. 



Although the fermentative action of micro-organisms has from 

 time to time attracted the attention of numerous investigators, both 

 chemical and biological, still in by far the majority of cases there has 

 been absolutely no guarantee that the chemical changes observed 

 were the result of the activity of a pure growth of one organism and 

 not of a more or less complex mixture of organisms. Indeed, it is 

 only within recent years that the most familiar of all fermentations — 

 the alcoholic — has been induced with growths of yeast definitely 

 ascertained to be of absolute purity. 



Thus whilst Pasteur and others had many years previously studied 

 the fermentation of sugar induced by yeast, free from bacteria and 

 other micro-organisms, it is to Hansen that we owe the systematic 

 investigation of the fermentations caused by distinct kinds of yeast in 

 a state of unquestionable purity. 



