AND ITS BEARINGS ON PATHOLOGY 377 
stantly streamed. The product, which by that time amounted to 54 drachms 
of clear watery liquid, had the sharp odour of the clot, but in a more concen- 
trated form. It was collected in three successive portions, the last of which 
had comparatively little of the sharp smell, and rather an odour like that of 
bread. That which first came off had such a sharply piercing smell that I felt 
no doubt that it was acid. To my surprise, however, I found it not only taste- 
less, but neutral to test-paper. I redistilled the product, and stopping the 
process when half had passed over, found the second distillate still more sharp 
in odour that the first, while the residue was almost odourless. But on distilling 
a third time I got a result less pungent than that of the second process, in con- 
sequence, I presume, of loss of some of the ingredient through extreme volatility. 
I kept the last distillate in a stoppered bottle for two days, at the end of which 
time it still retained its peculiar odour. What the nature of this substance 
is remains to be determined. It seems likely that it may be some ethereal 
product with the remarkable peculiarity of having an acid smell, though taste- 
less and neutral in reaction. 
It has been ascertained by Pasteur that the alcoholic fermentation, which, 
as we all know, consists in the main of the resolution of sugar into alcohol and 
carbonic acid without gain or loss of atoms, is attended with the appearance 
of other products in small quantity, such as glycerine and succinic acid, and 
the ethereal substance in souring milk may, perhaps, be related to the lactic 
fermentation in a similar manner. I cannot but think it likely that these 
apparently secondary products may, in reality, be of primary importance in 
the production of fermentative changes. Pasteur has shown that if yeast is 
added to a saccharine solution adapted for the nutrition of the Torula Cerevisiae, 
and the liquid is exposed in a thin layer in a shallow vessel to the atmosphere, 
the torula develops with peculiar rapidity, but little alcoholic fermentation 
results ; and, on the contrary, when the liquid is placed in a deep vessel in 
considerable mass, the torula develops comparatively slowly but gives rise to 
abundant fermentation. And he explains this remarkable result by supposing 
that the fungus requires oxygen for its nutrition, and when it cannot obtain 
it otherwise, abstracts it from the sugar, and so occasions the fermentation ; 
but when it can get the needful oxygen readily from the air, as it is able to do 
in the shallow vessel, it thrives peculiarly well, but, not having occasion to 
withdraw oxygen from the sugar, leaves it undisturbed, except the comparatively 
small portions of it which it assimilates for its own growth.? 
* Monsieur Pasteur expressed this view in 1861 in a Bulletin de la Societe Chimique, where, after 
relating the facts referred to in the text, he thus expresses himself :—‘ I] parait dés lors naturel d’ad- 
mettre que, lorsque la leviire est ferment, agissant a l’abri de lair, elle prend de l’oxygéne au sucre et 
que c’est la Vorigine de son caractére de ferment.’ In his recent work, Etudes sur la Biéve, 1876, M. 
