156 REpoRT OF DEPARTMENT OF BACTERIOLOGY OF THE 
SECURING THE ENZYM BY PRECIPITATION WITH 
ALCOHOL. 
Strong alcohol added to bacterial culture broths gives a 
flocculent whitish precipitate which includes not only the 
enzyms present, and various proteid matters, but also carries 
the bodies of the bacteria down with it. This is the com- 
monest method of securing enzyms in bacteriological investi- 
gations and is, therefore, in a measure a standard for com- 
parative work. ‘It also has advantages over the other meth- 
ods especially in that it is possible easily to preserve this 
dried precipitate for indefinite periods. For these combined 
reasons it was used in much of our work. We have found 
that 25 per cent of alcohol is fatal to the carrot-rot organism 
in broth cultures and since more than that amount was used 
in all our precipitation work, it is evident that this method 
insures the elimination of the living organism. 
METHODS. 
Several questions arose at the beginning as to methods 
which we will discuss under the following heads: 
1. Filtration—tThe first of these was as to whether the 
alcohol should be added directly to the culture broth, thus 
giving a precipitate containing the bodies of the bacteria, or 
whether it is preferable to remove the bacteria by passing 
the broth through a porcelain filter before precipitation. The 
trial reported on a preceding page showed that the filtered 
broth when tested directly possesses less enzymic activity than 
does the unfiltered broth. As is there shown, the precipitate 
obtained when such broth is rendered 80% alcoholic similarly 
has less enzymic strength than the precipitate from unfiltered 
broth. After a few trials had determined these facts all sub- 
sequent work along this line was with culture broths which 
had simply been passed through filter paper.* This filter re- 
“Some students of cytolytic enzyms have objected to the -use of filter 
paper because of the possible action of the enzym upon it. This occurred 
to us early in our work but repeated observations have shown this enzym 
is entirely inactive on the celluloses proper. We have, therefore, used 
Schleicher & Schull’s filter paper, both for es the broths and for 
collecting the precipitate. 
