Aug. i, 1921 
Studies in the Physiology of Parasitism 
621 
On the other hand, filtering the solution on which the fungus grew 
gave different results. Although most of the fungous material could be 
lifted from the flask, filtering was necessary before one could be reason¬ 
ably sure that no hyphae remained in the solution. Aside from the 
hyphae which were left in the solution, the liquid was reasonably clear 
and free of solid particles. To determine whether filtering removed any 
of the macerating principle, a number of experiments were made with 
solutions on which the organism had grown for about 40 hours at 37.5 0 C. 
The contents of two large flasks from which the fungous growth had been 
removed were mixed into one compound sample, one portion of which 
was filtered through a No. 2 Whatman chemically prepared filter paper, 
and another portion through a thick layer of absorbent cotton. The 
remainder served as a control, a portion of which was steamed 15 minutes 
to inactivate the enzym. Raw sweet-potato disks were then added to 
the different solutions and incubated at 37.5 0 . The results showed that 
the disks were macerated as quickly in the solution filtered through 
filter paper and cotton as in the unfiltered solution. 
Centrifuging. —Some investigators have removed the sand and 
fungus debris from the solution by centrifuging, a method well adapted 
to this type of work if an extract is required. This method is possibly 
open to the same objection as filtering the extract through filter paper 
in which it was shown that some of the macerating principle was removed. 
A comparison was made of the macerating power of the supernatant 
liquid of a centrifuged solution with that of the solutions of the same 
origin filtered through filter paper, through cotton, and not filtered. 
The experiment was carried out by the use of 0.5-gm. samples of hyphae 
ground in sand and extracted for 18 hours in 25 cc. of distilled water. 
At the end of 18 hours the contents of some of the flasks were centri¬ 
fuged for 5 minutes, and the supernatant liquid was used for macerating 
experiments. The contents of some of the other flasks were filtered 
either through filter paper or through cotton. The remaining flasks 
were not filtered and served as controls. The results showed that macera¬ 
tion was complete in the solution not filtered or centrifuged in 3.5 hours, 
in the centrifuged solution in 4 hours, and in the filtered solutions in 
5 hours. 
Relation to sunlight. —Light is said to be injurious to certain 
enzyms. In view of the fact that most of the mechanical operations of 
the present investigations must be carried out in diffused light, in some 
cases the enzym powder being exposed to the light for a considerable 
length of time, it was thought advisable to determine what effect, if 
any, such exposure had on the macerating power of the enzym. These 
experiments were carried out by exposing for 2 hours lots of 0.25 gm. 
of hyphae to direct sunlight and diffused light and placing some in an 
incubator in which light was practically excluded. In some experiments 
