52 Proceedings of Royal Society of Edinburgh. [sess. 
investigate the growth of a series of organisms on media coloured 
with litmus, and found, to my great perplexity, that a certain number 
reddened it, but only at a definite temperature which varied with 
the organism and the medium under consideration. Belatively 
larger quantities of acid than ammonia ('?) appeared to be formed only 
within a certain range of temperature. Warrington * found, with 
quite a series of organisms, that when cultivated in milk, at higher 
temperatures they produced relatively more ammonia, at lower re- 
latively more peptone. It has been recently communicated that 
certain yeasts produce at lower temperatures relatively more alcohol, 
at higher temperatures relatively more glycerine. The one dis- 
sociation appears to be favoured at a higher, the other at a lower 
temperature. I conclude that the temperature acts more or less 
directly on those catalysing processes inherent in the protoplasm 
itself, in a way similar to that in which it acts on the enzymes 
which are separable from the protoplasm. It has already been 
noted, that in the organisms of the cholera group the rennet-like 
ferment appeared able to act in acid reaction in which the pepsin- 
like ferment was inhibited. We should not then be surprised to 
find that a chemical substance is able to inhibit one catalysing 
process in the protoplasm without materially affecting the others. 
There are already many facts in Bacteriology which speak for this, 
but a systematic examination of the influence which such bodies 
exert on the functions of microbes is much to be desired, as throw- 
ing light upon the way in 'which a drug affects the reactions of the 
living protoplasm, and as furnishing us with a basis on which a 
cellular therapeutics may perhaps in the future be founded. Interest- 
ing as this subject is, it cannot now be further entered upon in a paper 
whose proper theme is the enzyme function in its relation to the 
general physiology of the cell. 
In conclusion, I wish to acknowledge my great indebtedness to 
Professor Ferdinand Hueppe, not merely for invaluable assistance in 
the experimental work, but also for the general biological outlook, 
I have here adopted. My thanks are also due to Dr Woodhead, for 
wliat we may term the solidarity of the organism, has never yet received the 
attention which it deserves as a factor which may determine the degree of fixity 
of a new adaptation. 
* Journal of the Chemical Society , 1888. 
