But whilst the easy access of bacteria for experimental and scientific purposes is of great importance to the investigator, their indiscriminate distribution would equally be a source of uneasiness and danger to the community at large. Already sensational fiction has made considerable capital out of the pathogenic microbe, and with the winged aid of penny publications it does not take long for suggestions of such kinds to spread in society and assume practical shape, and whilst the administration of bacterial poisons offers comparatively but little difficulty, their identification would be a far greater problem for experts than that presented by particular chemical poisons. To cope with this danger to the public, specimens of disease-germs from these bacterial depôts may not be supplied to applicants unless the latter can prove to the satisfaction of the director that they are connected with responsible public institutions. In recent times, indeed, one of the most remarkable practical uses to which bacteria have been put is that of poisoning-agents on a large scale, or in other words vermin exterminators; if this new rôle for bacteria becomes extended, as no doubt it will, the law for the sale of noxious drugs and preparations will also doubtless be amended to cover the distribution of bacterial-poisons. It was in the year 1889 that Professor Loeffler, while experimenting with mice in his laboratory at Greifswald, discovered a micro-organism which was extremely fatal to all kinds of mice. The happy idea occurred to the Professor that this lethal little microbe, which he christened _Bacillus typhi murium_, might be turned to excellent account in combating plagues of field mice in grain-fields, where the devastation committed by these voracious rodents had become in parts of Greece and Russia a serious source of loss to agriculturists. Experiments were accordingly made on a small scale to test the efficiency of this bacterial poisoner in destroying field mice, and so successful were the results that Loeffler confidently announced the possibility of keeping down these pests by distributing food material infected with these bacteria over fields which were invaded by them. The Greek Government took up the question, and Loeffler's method was applied with brilliant results; the disease was disseminated with extraordinary rapidity and severity, and the mice were readily destroyed.