Such results naturally only served to whet the scientific appetite for more, and the liquefaction of air and of hydrogen placing much lower temperatures at the disposal of investigators, those bacteriologists who were fortunate enough to command a supply were not long in availing themselves of the opportunity thus given them of further testing the vitality of micro-organisms. Botanists had already shown that exposure to liquid air, which means a temperature of about -190° C., and to liquid hydrogen, which means a temperature of about -250° C., did not impair the germination powers of various descriptions of seeds, such as those of musk, wheat, barley, peas, vegetable marrow, and mustard, and that their actual immersion in liquid hydrogen for the space of six hours did not prevent them coming up when sown just as well as ordinary seeds which had not undergone this unique experience; hence the opportunity of submitting other members of the vegetable kingdom to these low temperatures was eagerly sought for by bacteriologists. Dr. Macfadyen found this opportunity in the laboratories of the Royal Institution, and, Professor Dewar having placed a generous supply of liquid air and liquid hydrogen at his disposal, he submitted specimens growing in various culture-materials, such as gelatin, broth, potatoes, etc., of typhoid, diphtheria, cholera, anthrax with spores, and other bacteria, for twenty hours and seven days respectively, to a temperature of about -190° C. In no instance, however, whether exposed when growing in fluid or solid media, could any impairment of their vitality or the slightest alteration in their structure be observed. Similar results were obtained when liquid hydrogen, or a temperature of about -250° C., was applied. The question of the retention or otherwise of the disease-producing powers of these bacteria was not investigated, and in this connection much interest attaches to Mr. Swithinbank's investigations on the vitality and virulent properties of that notorious malefactor amongst micro-organisms, the _bacillus tuberculosis_, when exposed to the temperature of liquid air. The specimens of the consumption bacillus employed were originally obtained from the human subject, and they were exposed for periods varying from six hours to six weeks to -190° C. In each case the malignant properties of the tubercle bacillus after exposure were tested by their direct inoculation into animals, and the results compared with those which followed similar inoculations made with bacilli which had not been frozen in this manner, but had been grown in ordinary circumstances. In no single case, Mr. Swithinbank tells us, were these frozen tubercle bacilli deprived of their virulence, and the length of exposure, at any rate as far as could be judged after six weeks, appeared to make no difference in this respect. It is true that the pathogenic action of the frozen bacilli appeared to be