254 Prof. M. C. Potter. Bacteria ds [Jan. 18, 
absorbed. After this treatment the vitality of the seeds was not impaired 
nor their power of germination. Further, the semi-permeable covering 
enclosing these seeds permits the absorption of water from weak solutions of 
acids and alkalies, while excluding the latter compounds; but it does not 
prevent the passage of iodine. 
An important question raised by these investigations is : to what extent are 
plants in general protected by this means, and may it be that some bacteria 
may possess a cell-wall of a semi-permeable nature which acts as a protective 
envelope and so accounts for the immunity from injury which many species 
possess? Some observations I have made on the behaviour of certain bacteria 
in solutions of mercuric chloride seem to indicate that this might be so. 
Plainly, they have some means of protection against a strong solution of such 
a poison, but it proved too difficult a piece of microscopy to determine whether 
the sublimate was actually excluded by the enclosing membrane. 
The well-known oligodynamic theory of Nigeli(5) may also be cited as 
bearing upon the effect of antiseptics in certain cases. His observations show 
that the toxic action of poisons is reduced in the presence of certain insoluble 
substances such as graphite, etc. True and Oglevee (13) have more recently 
extended the work in this direction and entirely in favour of Nageli’s con- 
clusions. Their results establish the fact that the presence of certain insoluble 
substances tends to decrease the toxic activity of solutions of strongly toxic 
compounds; and their experiments with mercuric chloride prove that the 
presence of insoluble bodies modifies very markedly the toxic influence of this 
salt upon the roots of seedlings. The theory advanced is the attraction of 
the ions, or molecules, of the dissolved substances for the solids and their 
absorption by the latter. 
An explanation is thus afforded of the snecieney of a high percentage of 
corrosive sublimate and the behaviour of iodine as an antiseptic, in the presence 
of finely-divided coal and charcoal. The insoluble nature of the research 
material, and the possibility of a semi-permeable or selective property of the 
bacterial cell-wall, appear to offer an intelligible interpretation of the un- 
certain effect of the antiseptics employed in this research. 
The whole question of the dependence upon antiseptics requires considera- 
tion, and it is evident that the efficiency of any one cannot be taken for 
eranted, but must be tested for the special conditions under which it is 
employed. 
Lately, Stoklasa(11) has published a preliminary note upon the oxidation 
of coal and charcoal, and concludes from comparative researches upon 
“sterile and non-sterile ” coal that the evolution of CO is due to: (1) Auto- 
oxidation, (2) the action of an enzyme. The theory of auto-oxidation is not 
