reveal themselves in the jelly according to the number and kinds of utterly invisible parent microbes introduced by your “washings” into the jelly. And so the investigator has the means of getting at each kind of invisible microbe quite detached from the others, and of separating it for further cultivation and experiment as to its chemical and disease-producing qualities. These microbial gardens of jelly-plates are, indeed, a wonderful revelation and a fitting “horticultural” accompaniment to the dark and gloomy forests of rampant wild microbes in our insides, where all are struggling for the soil, one crushing out another by its sheer exuberance, a third choked by the encircling luxuriance of a fourth, just as the trees, mosses, and climbers of a tropical jungle are budding, pushing, grasping, destroying one another in their irrepressible growth. Pettenkofer, of Munich, when he found (as Metchnikoff did later) that the cholera-bacillus could be swallowed in spoonfuls without producing any harm, came to the conclusion that, though it was a necessary agent of the disease “cholera,” yet that there was still an unknown additional determining “cause” of a local character which must be present in order to render the “cholera-bacillus” effective. Metchnikoff is now seeking this “local” cause and parallel antagonistic causes, in the microbian flora of localities which locally effect an entry into the human body, and are, on the one hand, “favourable,” or on the other hand “antagonistic.” Take as a concrete example Versailles. When cholera has been rife in Paris, there has been no cholera at Versailles. There is something at or about Versailles which does not permit cholera to flourish in men who live there. The guess—the hypothesis—which is being investigated at this moment, is that there is possibly a microbe present at Versailles which enters into the microbial jungle of the intestine of mankind there, and is inimical to, repressive of, the cholera-bacillus when it also arrives there. Similarly, the suggestion is entertained, and is being experimentally tested, that there is in Paris a microbial inhabitant of the intestine which is favourable to the energetic growth of the cholera-bacillus when it puts in an appearance, but that this favouring (as yet undetermined) microbe does not exist at Versailles. These imaginings and guesses as to favouring and antagonising microbes must not be confused with the definitely ascertained facts as to the cholera-bacillus. But they are quite sufficiently important and probable to justify their narration to a discreet and sympathetic public. XXVI SEA-BREEZES, MOUNTAIN AIR, AND OZONE