William Brown. 
116 
by mechanical agitation, and by neutralisation with alkali. The 
extracts so deactivated possess no lethal activity whatever. From 
microscopical investigation it is known that death of the cell takes 
place at a late stage in the process of disintegration of the cell 
walls. The latter process is therefore the determining factor of the 
whole action, that is, there is or is not lethal action according as 
there is or is not previous macerating action. This dependence of 
lethal upon macerating activity may be explained according to a 
variety of hypotheses. 
(1) That there is no distinct lethal substance but that death of the 
cell follows on account of the physiological derangement caused by the 
disorganisation of the cell wall. This hypothesis is unlikely in view 
of the rapidity with which death of the cells takes place. It is 
known from plasmolytic studies that the association of cell wall and 
protoplasm can be broken for many hours without death of the cell 
ensuing. The rapid effects obtained in the present case cannot, 
therefore, be ascribed to this cause. 
(2) That the toxic principle is produced by action of the 
macerating principle on the cell wall, and does not exist, therefore, in 
the initial extract. This view must be abandoned in the face of 
experimental evidence that extract in which a considerable quantity 
of cell wall has been digested behaves identically in all respects with 
the original extract. 
(3) That the two actions are due to different substances, but the 
lethal substance is unable to reach the protoplast until the permeability 
of the cell wall has been sufficiently increased by the action of the 
macerating substance. If there be a lethal as distinct from a macer¬ 
ating substance, it must possess the following characteristics. From 
the diffusion experiments with gelatine, above mentioned, it must 
possess a diffusive capacity at least equal to that of the macerating 
substance ; also it cannot be crystalloidal, and in particular it cannot 
be a soluble oxalate. From the data regarding extracts which have 
been deactivated in various degrees by heat, mechanical agitation, 
neutralisation with alkali, it is clear that the lethal substance, if 
present, must remain in the deactivated extracts (it cannot be 
assumed to show exactly the same sensitiveness in these respects 
as the macerating substance). The lethal principle must thus be 
assumed to be present in deactivated extracts, though it cannot act 
in virtue of its inability to diffuse through the unaltered cell wall 
Killing of the cells should then continue independently of the 
macerating action after a certain stage is reached, that is when th e 
