is by no means easy of estimation, and that numerous and very varied factors have to be taken into account when we attempt to endow it with any measure of practical hygienic import

ance.

In connection with the vitality of anthrax germs in water, which has afforded material for so many laboratory investigations, it is of interest to consider what chance exists of anthrax being communicated by water. Until a few years ago, as far as I am aware, no instance had been recorded of anthrax having been actually communicated by water, until an outbreak of anthrax on a farm in the south of Russia was distinctly traced by a skilled bacteriologist to the use of water from a particular well, in the sediment of which the bacillus of anthrax was discovered.

Anthrax bacilli have also been detected in the water of the River Illinois in the vicinity of Chicago, one of the chief sources of pollution of which is the slaughtering of cattle and the discharge of their offal into the river.

The likelihood of such contamination taking place through the drainage of soil makes it of importance to ascertain what may become of the bacilli of anthrax derived from the bodies of animals which have died of this disease, and whose carcasses have been buried and not burnt.

The anthrax bacillus cannot produce the hardy spore form within the bodies of animals, but it does outside. Now it has been shown that the bacilli of anthrax taken from the blood of an animal dead of anthrax are destroyed rapidly in ordinary River Thames water, for example, but that if the temperature of the water to which they gain access is somewhat higher than usual, such bacilli are able to sporulate or produce spores in the water, and in that hardy form can retain their vitality and virulence for several months.

That anthrax bacilli can produce spores in water under certain conditions has not hitherto been dwelt upon in discussing the question of their vitality in water, and it is of obvious importance in connection with the action of sunshine on anthrax germs in water, knowing as we now do the very different manner in which the spores and bacilli respectively behave when under the influence of the sun's rays.

It was not, perhaps, unnatural that rash assumptions as to the efficacy of sunshine should have been readily accepted when such remarkable feats performed on microbes by sunshine were being continually put forward.

Thus it has been found that insolation, even when it does not destroy, may effect profound

changes in the physiological character of certain micro-organisms.

Dr. Lohmann, of Rostock, discovered that some hours' exposure to bright sunshine entirely destroys yeast cells, whilst even feeble and intermittent sunshine is capable of paralysing them, and that they only recover their vitality when removed from this obnoxious influence. This recuperative power is not, however, shared equally by all varieties of yeast, some possessing it in a far greater degree than others. Dr. Lohmann also found that yeast cells, after being exposed to sunshine, assumed a shrunken and distorted appearance, showing that insolation had produced a striking physiological effect upon the structure of these cells.

Professor Hansen published some years ago a most interesting memoir on some of the characteristic features of the moulds which are to be found on manure heaps, in which he records how light exerts a very important influence on the manner in which the spore or fruit of these lowly vegetables is set free or distributed. All the various phases in the fructification process of some of these moulds were carefully watched by Dr. Hansen. He kept his caged specimens near a window with an eastern aspect, and he states that in the first instance the stalks inclined towards the light, but that afterwards they

assumed an upright position. Darkness was nearly always chosen for the liberation of the spores, but in a few instances a small number were released during the daytime, and it was noticed that when this did occur they were invariably discharged on the side away from the source of light. In various other ways he confirmed this interesting observation, and found that the fruit of the mould was invariably discharged in the opposite direction to that in which the stalk had previously inclined under the influence of light. The force with which the spores were discharged varied very considerably, sometimes being cast to a distance of four inches or more from the stalk, and sometimes being found close to and even on the stalk. The manner in which sunshine may also modify the pigment-producing powers of micro-organisms is remarkable.

Many microbes are able to elaborate when grown on various culture media, such as gelatine or slices of potato, most brilliant and beautiful pigments ranging from intense blood-red to the most delicate shades of pink, and embracing every gradation of yellow, as well as browns, greens, and violets. Now it has been found that some of these pigment-producing bacteria, when exposed to sunshine on these nutritive materials, fail to exhibit their characteristic colour, although the duration

G

of insolation may not have sufficed to destroy their actual vitality. One of these organisms originally obtained from water has been specially studied in this respect by M. Laurent. If slices of potato are streaked with a small number of this particular bacillus (bacille rouge de Kiel) a magnificent patch of blood-red colour makes its appearance in the course of a day or two, but if, on the other hand, similar slices of potato are exposed to three hours' sunshine, a colourless growth subsequently develops, except where here and there a few isolated spots of pale pink are visible. When the insolation is prolonged for five hours nothing whatever appears on the potato, the bacilli having been entirely destroyed. But this is not all. M. Laurent found that if he took some of the colourless growth and inoculated it on to potatoes he obtained again, but without insolation, a colourless vegetation-in fact, three hours' insolation had so modified the physiological character of the bacillus that a new race had been generated, a race deprived of its power of producing this red pigment. In what numerous directions the character of microbes may be and are being modified, even by simple exposure to sunshine, opens up a wide field for speculation and research, whilst the tractability of these minute and most primitive forms of life, if we only approach their