Aug. i, i92i Studies in the Physiology of Parasitism 613 
METHODS OF EXPERIMENTATION 
The investigations as outlined involved a study of the macerating ac¬ 
tion (1) of the enzym contained in the hyphae and (2) of that exuded from 
the mycelium into the culture solution. Brown (4) worked principally 
with the extract of the fungous material, although he domonstrated the 
excretion of the active principle into the culture medium. While offering 
no criticism upon the employment of the fungous extract, the writers 
have carried out macerating experiments with the solution on which the 
fungus grew as well as with the powdered hyphae. The use of the solu¬ 
tion offered no mechanical obstacles, since to obtain fungus material the 
organism was grown on a liquid medium. Furthermore, in view of the 
fact that the macerating action is due to an enzym which diffuses out of 
the hyphae, it seemed to the writers that the macerating power of the 
solution should be studied concomitantly with that of the hyphae. 
CULTURE MEDIUM 
Since both the intracellular and extracellular pectinases were to be 
studied, a liquid medium which would support a rapid and luxuriant 
growth in a relatively short time and which would be available at all 
times of the year so that the investigations could be carried out without 
interruption was found to be preferable. The enzyrns which diffuse out 
from the hyphae become dispersed throughout the medium, and after 
the liquor is freed of the mycelium it is ready for the macerating experi¬ 
ments. The medium which was finally employed was a decoction made 
from sweet potatoes prepared by the following formula: To the peeled 
potatoes add double the weight of water, steam for one hour, then squeeze 
out the liquid through gauze; steam a second time, filter by suction 
through absorbent cotton, add the required amount to flasks, plug with 
cotton, and autoclave for 20 minutes at 15 pounds pressure. The re¬ 
sulting solution is practically free of cellular structures but does contain 
some starch and some sugars. 
In this medium a felt or mat composed of fungous threads, floating 
for the most part on the surface, which can readily be lifted from the 
liquid, is formed in from one to two days. 
In view of the fact that a large quantity of mycelium was frequently 
necessary, 2-liter Erlenmeyer flasks containing 250 cc. of the decoction 
were used. If more than one flask was used the hyphae from all of them 
were made into one compound sample. The maceration of the raw 
sweet-potato disks was carried out with a weighed amount of this sample 
suspended in a definite amount of distilled water. Accordingly the 
solutions from all the flasks on which the fungus grew were collected 
into one flask, thoroughly mixed, and the maceration was carried out 
with a measured quantity. 
