Fellow of the Botanical Society, Edinburgh, Corresponding Member of the Botanical Society Of Canada, Surgeon to the West Norfolk end Lyan Hospital.

It is now more than twenty years since it was first discovered that vegetable growths could exist upon the human body. From the earliest age diseases of the skin were known and described: the symptoms and appearances they presented were matters of ordinary observation, and rules of an empirical character were laid down for their treatment.

During all this time, it is probable, nay, almost certain, that in some forms of the disease fungi were constantly present, but it was not until the year 1889 that this fact was demonstrated. To M. Schoenlein, of Berlin, we are indebted for this most important discovery, which, but for the rapid advance that has been made in scientific knowledge during the present century, and above all in the prop- er use of the microscope, would, like many other wondrous things, be still one of nature's own secrets. Even now, strange to say, there are those who regard the growth described by Schoenlein as an abnormal production of the body, and deny its vegetable origin; but a vast amount of accumulated evidence leaves no room for doubt upon this point, to any one who is at all conversant with the character, structure, and behavior of the humblest individuals of the plant world, the Fungi.

Regarding it, then, as an established fact, with botanists and the medical pro-fession generally, that a fungous growth is really present in the majority of skin diseases, I shall abstain from entering on the discussion of the reason for upholding this opinion, and leave the facts, to be presently mentioned, to speak for themselves; suffice it to say here, that men of the greatest eminence as botanists and physiologists entertain no doubt on the subject.

We have, however, another and a larger class of observers, who, while they admit the presence of the fungus, disclaim for it any title to be considered as an originator of disease, but regard it rather as a foreign and accidental visitor, engendered and fostered by the products of a pre-existing malady. Upon this more important dogma, which has, in this country, been the subject of much argument, I propose to speak at greater length, inasmuch as it is a question of considerable interest, in a medical and hygienic point of view.

Before doing so, however, let me point out some of the various forms of fungi which have been noted, as occurring upon animal organisms, in order that I may put before you the salient points which are worthy of interest and attention. The whole of these lower fungi are ascribed by botanists to a subdivision of the family, which has received the name of Hypomycetous. They are minute microscopic plants, consisting, in their perfect state, of a mycelium, that is, a net-work of fine capillary tubes or filaments, from which springs an upright, hair-like stalk bearing at its extremity a collection of spores or sporules - the seeds of the plant. These have a diameter of about 1/3000 of an inch, and from their extreme (lightness are capable of floating about in the atmosphere, and are wafted by the air to every quarter in incalculable myriads.

Whenever they alight upon* objects favorable to their growth, as upon decomposing organic matter of any description, they readily germinate, provided there be sufficiency of warmth and moisture, both of which are essential to their welldoing.

Let us follow one of these spores, thus located, and watch its development; we shall then have the key to the behavior of the rest. When first given off from the fruit-stalk it is a spherical cell, consisting of a cell-wall filled with homogeneous molecular plasma, but without a nucleus; on the application of warmth and moisture the cell assumes, in the first instance, an oval form; the cell-contents become granular, the granules ultimately coalescing to form one or more nuclei. In its next stage, it becomes elongated, until its length exceeds its breadth by two or three times, and now we observe small eminences arise from its extremities; these are buds, which, in their turn, become elongated cells, and then give off other buds or shoots, each in succession acquiring additional length, until, finally, we find them as filaments or thread-like cells, crossing each other in all directions, and forming a network which is termed the mycelium.

At a more advanced stage, these filaments are seen to contain mumerous nuclei and granules, and now, several slender threads are pushed perpendicularly upwards; these are fruit-stalks, the terminal cell of which undergoes budding or segmentation, until a large number of spores is formed into a capitulam or head. These, like the original cells we started with, are spherical, and their arrangement varies in different genera; for example, being collected into a round head or glomerulus, as in Mucor; or into a brush-like one, as in Aspergillus, so named from a fancied resemblance to the brush used for sprinkling holy water in Roman Catholic Churches.

Such is, briefly, the mode of development of these minute plants under favorable conditions. But there are occasional deviations to be met with, which are deserving of attention, as throwing a clearer light upon certain forms which are to be mentioned presently. This will be manifest when I state that, from the results of numerous experiments I have made, the plant may be caused to remain in any one of its different stages of growth by supplying it with food suitable for that purpose. The bearing of this statement will be seen in the subsequent remarks upon the identity of the parasitic fungi. A familiar illustration of the power above mentioned is to be observed in common yeast, which presents itself as a collection of spherical cells containing nuclei, and capable of endless multiplication in two ways, viz: by the formation of buds, or by the bursting of the cells and the liberation of nuclei, which become cells. Yeast is derived from the aerial spores of one or more common species of mould.