On the Physiology of Parasitism. t i 5 
regards its action on the cell walls and on the protoplasmic contents 
is totally destroyed by a sufficient degree of heating. Deactivation 
by heat is very rapid at 60°C. At 65°C it is as near as may be 
instantaneous. 
b. Relation to Mechanical Shaking. The extract can be 
deactivated by agitation, e.g., either by shaking in a closed vessel 
or by bubbling a stream of air (or nitrogen) through it. The effect 
is quite marked at ordinary temperatures (15-20°C), but increases 
very rapidly with rise in temperature. 
c. Relation to Diffusion. The extract was submitted to 
diffusion through a series of graded gelatine membranes prepared in 
the first instance after the method of Bechhold (4) and later 
according to the writer’s method (5). Dialysates containing various, 
concentrations of the active principle were thus obtained. All the 
dialysates which showed an action on the cell wall of tissue were 
also active in killing the cell contents. 
From a series of comparative diffusion experiments it was 
shown that the active principle of the extract possessed a coefficient 
of diffusion through gelatine comparable with that of dextrin and 
somewhat greater than that of diastase. 
Dialysis of crystalloidal contamination from the active principle 
was effected by the use of a certain type of collodion thimble (6), as 
well as by means of gelatine membranes of high gelatin content. 
The dialysate was found to show no action either on the cell walls 
of tissue or on the protoplasmic contents. 
The dialysate was found to contain a small amount of a calcium 
salt in solution. The presence of a soluble oxalate in the extract, 
even in minimal quantity, is thus excluded. 
Conclusions as to nature of Active Principle. 
The action of the fungus and fungal extract on tissue' has been 
seen to consist of an action on the cell walls together with an action 
on the living protoplasmic contents. These actions must be 
assumed a priori to be different in nature and to be brought about 
by different agents. For convenience of discussion we shall there¬ 
fore speak of the “macerating” and “lethal” principles of the 
extract, these being responsible respectively for the macerating 
action ( i.e ., action on the cell walls) and lethal action (i.e., action on 
the living protoplasm) of the extract. 
It has been shown in the foregoing that the macerating action 
of the fungal extract can be destroyed in various ways: by heat, 
