Brown .— Studies in the Physiology of Parasitism . /„ 337 
As in the case of heat deactivation, it was found that no separation of 
macerating and lethal actions could be effected by this means. 
Relation to Diffusion and Dialysis. 
The experiments on this subject are not yet completed, and it is 
therefore proposed to give certain results only in rlsuml. 
Comparative diffusions were carried out by means of a series of graded 
gelatine (5, 10, 15, 20 per cent.) membranes prepared after the method of 
Bechhold. From these experiments it appeared that the macerating 
principle possessed a coefficient of diffusion comparable with that of dextrin 
and greater than that of diastase. It is thus a colloid of intermediate type. 
Again, all the fungal extracts which have been purified by diffusion through 
gelatine membranes showed a normal lethal activity, and though it has not 
been possible as yet to perfect the experiments in this connexion, there is 
a strong presumption that if the diffusate possesses any macerating activity, 
it possesses likewise lethal activity—in other words, if there are two 
principles concerned, the diffusive capacity of the lethal principle is not less 
than that of the macerating one. 
A complete dialysis of the macerating principle was effected by the use 
of a certain type of collodion thimble. In this case it was found that the 
macerating principle could be completely held back. On testing the 
dialysate, after removal by means of the air-pump of the volatile antiseptic, 
no trace of a killing action was shown. Subsequent control experiments 
with the same membranes showed that they were quite permeable to 
crystalloids such as cane sugar, ammonium oxalate, &c. 
By this dialysis method a very convincing proof was obtained that 
soluble oxalates do not play any part whatever in the lethal activities of the 
extract. The dialysate from the collodion thimbles gave a precipitate with 
potassium oxalate solution, thus showing the presence of a substance 
(presumably a calcium salt) which precipitated oxalates. Control experi¬ 
ments showed that this substance was not derived from the membrane 
itself. It was accordingly present in solution in the continuous phase of the 
colloidal extract, so that the simultaneous presence of a soluble oxalate was 
quite excluded. 1 
1 This dialysis experiment was in one case carried out with the following precautions: The 
collodion membranes were never allowed at any time to come into contact with tap-water. The 
germinated spores were subjected to prolonged washing in distilled water and dried in vacuo over 
sulphuric acid. The dried material was ground without sand, a control experiment having shown 
that no calcium was derivable from the mortar. With extract from this material it was also found 
that calcium could be demonstrated in the dialysate. Since these precautions for excluding 
contamination with traces of calcium were not usually adopted, it is safe to assume that the presence 
of a soluble calcium salt can be predicated of all the extracts that have at different times been 
employed. Whether the calcium salt is derived from the contents of the fungus cells or is strongly 
adsorbed on the walls from the liquid in which germination took place, it is impossible to say. 
