48 
MR. J. R. GREEN ON THE CHANGES IN THE PROTEIDS 
3. What is the influence of alkalis and neutral salts on the ferment f 
The complete absence of any sign of activity in the alkaline tubes suggested, as the 
third point, an enquiry as to what had happened to the ferment in these; that is, 
had its activity been merely suspended, or had it been destroyed as is the case on 
similar treatment of pepsin ? # To determine this point, which had rather an 
important beai’ing on subsequent work, the two tubes D and F in the last series 
of experiments were made the subject of further investigation. 
D contained the ferment in 1 per cent. Na. 2 C0 3 solution. It had been shown to 
be inoperative on fibrin in such a fluid. If its action were only suspended, it would 
be able to digest fibrin if the reaction were made acid to about the extent of "2 per 
cent. HC1. If it had been destroyed, such treatment would not restore the activity. 
At the same time, by the neutralisation of the Na 2 C0 3 , some salt would be formed 
which might or might not have an influence on its rate of activity, should such exist. 
The contents of the tube were therefore carefully neutralised, and the alkali- 
albumin referred to consequently precipitated. It seemed possible that any ferment 
present might be carried down by this precipitate, as such bodies do generally 
accompany precipitates in the fluid in which they are present. Only half the liquid 
was consequently filtered. Both were then added to an equal bulk of '4 per cent. 
HC1, and a fresh measure of fibrin added to each. The little quantity of the 
dissolved alkali-albumin in the unfiltered tube would not interfere with the result, 
as the activity was judged of by the disappearance or not of the fibrin. The filtered 
tube was labelled Lfi and the unfiltered one Ik. 
It was of course necessary to control the experiment by having two precisely 
similar tubes containing ferment that differed from these only in not having been 
exposed to the action of the alkali. It was necessary, therefore, to add to these 
exactly the same amount of neutral salt which Iff and D 2 contained. This was done 
as follows :— 
50 c.c. of Na 2 C0 3 solution 1 per cent, were taken, and 5 c.c. dialysed ferment 
extract added. This reproduced the condition in D at commencement of the former 
experiment. Instead of allowing the alkali to act on the ferment, the mixture was at 
once made neutral. There was present now the same amount of salt as in D after 
digestion and subsequent neutralisation. The liquid was a little turbid from presence 
of a little proteid matter in the extract used. Half of it was filtered and half left 
unfiltered. 27’5 c.c. of "4 HC1 and a measure of fibrin as before were now added to 
each ; they were labelled D 3 and D 4 , and the 'whole set placed on a water bath. 
The digestion was tested ns it proceeded, but no marked results were obtainable for 
a longer time than usual. The digestion was allowed to proceed for 54 hours, when 
the following results were noted :— 
* Langley, ‘ Jcrarn. of Pliysiol.,’ vol. 3, p. 24G. 
