MEANS OF DEFENCE AGAINST MICROBES. 255 
this latter dose is a maximum which it is almost 
impossible to exceed in man in the course of twenty- 
four hours without poisoning him, 
Sulphurous acid is very effectual when employed 
in fumigations, but it does not penetrate to the interior 
of the tissues, and only acts on the microbes on their 
surface. It does not destroy their spores. 
Iodine has great effect in this respect. Davaine 
has ascertained that seven milligrammes of iodine 
suffice to destroy the bacteria of anthrax in a litre 
of liquid. Instead of a hot iron, tincture of iodine 
might, therefore, be used to cauterize the bites of 
poisonous flies, carbuncles, and the pustule of anthrax. 
Koch states that a solution of five per cent. of 
carbolic acid is required to destroy the spores of 
anthrax in twenty-four hours; but the bacilli them- 
selves are destroyed by a solution of one per cent. 
A solution of 0:02 per cent. iodine, or 0:07 per cent. 
of bromine prevents the development of bacilli. 
Chloride of zinc and sulphate of iron, which have 
been recommended as disinfectants, are very inferior 
to chloride of lime, which takes the third place in the 
list, the second being occupied by chlorine. 
Alcohol arrests the development of bacteria and 
theif spores, but does not destroy the latter, even 
at the end of a month, as it is stated by Claude 
Bernard. 
Babés regards essence of mustard as an excellent 
preservative from cholera. If a drop of this essence 
