Going back to my earlier experimental researches to determine the part taken by saccharomycetes and saprophytes in fermentation, I find, from correspondence in my possession, that in 1859 I demonstrated to the satisfaction of Dr. Bell, F.R.S., the then head of the chemical laboratory of Somerset House, that a very small portion of putrefactive matter taken from an animal body, a parasitic fungus (Achorion Schöenleinii), a mould (Aspergillus or Penicillium), and a yeast (Torula cerevisiæ) would in a short time, and indifferently, set up a ferment in sweet-wort and transform its saccharine elements into alcohol, differing only in degree (quantitative), and not in kind or quality. This, then, was the first step in the direction towards proving symbiotic action between these several parasitic organisms. The only apparent difference observed during the fermentative processes was that putrefactive (saprophytic) action commenced at a somewhat earlier stage, and that the percentage of alcohol was also somewhat less.[51]
In 1856, also, the ærobic bacteria attracted my attention, and, together with the late Rev. Lord Sidney Godolphin Osborne, I exposed plates of glass (microscopical slides), covered with glycerine and grape sugar, in every conceivable place where we thought it possible to arrest micro-organisms. The result is known, viz., that fungoid bodies (moulds and bacterial) were taken in great numbers, and varying with the seasons. The air of the hospital and sick-room likewise engaged attention, each of which proved especially rich in parasitic bodies. During the cholera visitation of 1858 the air was rich in ærobic and anærobic bacteria, while a blue mist which prevailed throughout the epidemic yielded a far greater number than at any former period (represented in [Plate I]., No. 13). This blue mist attracted the especial attention of meteorologists. At a somewhat later period a more remarkable fungoid disease, the fungus foot of India, mycetoma, came under my observation, a detailed description of which I contributed to the medical journals, and also, with further details, to the “Monthly Microscopical Journal” of 1871. Interlacing mycelia, ending in hyphæ, in this destructive form of parasitic disease were seen to pervade the whole of the tissues of the foot, the bony structures being involved, and it was only possible to stay the action of the parasite by amputation.
So far, then, the study of parasitic organisms had at an early period shared largely in my microscopical work, extending over several years, and with the result that these micro-organisms were found to exhibit on occasions great diversity of character, and that different members of the bacteria in particular flourish under great diversity of action, and often under entirely opposite conditions; that they feed upon wholly different materials, and perform an immense variety of chemical work in the media in which they live.
The study of the chemistry (chemotaxis) of bacteria has, however, greatly enlarged our conception of the chemical value and power of the vegetable cell, while it is obvious that no more appropriate or remunerative field of study could engage the attention of the microscopist, as well as the chemist, than that of bacterial life, and which is so well calculated to enlarge our views of created organisms, whether belonging to the vegetable or animal kingdom.
Pathogenic Fungi and Moulds.
It is scarcely necessary to go back to the history of the parasitic fungi to which diseases of various kinds were early attributable. The rude microscopes of two and a half centuries ago revealed the simple fact that all decomposable substances swarmed with countless multitudes of organisms, invisible to ordinary vision. Leuwenhoek, the father of microscopy, and whose researches were generally known and accepted in 1675, tells of his discovery of extremely minute organisms in rain-water, in vegetable infusions, in saliva, and in scrapings from the teeth; further, he differentiated these living organisms by their size and form, and illustrated them by means of woodcuts; and there can be no doubt that his figures are intended to represent leptothrix filaments, vibrios, and spirilla. In other of his writings attempts are made to give an idea of the size of these “animalcules”; he described them as a thousand times smaller than a grain of sand. From his investigations a belief sprung up that malaria was produced by “animalcules,” and that the plague which visited Toulon and Marseilles in 1721 arose from a similar cause. Somewhat later on the natural history of micro-organisms was more diligently studied, and with increasing interest. Müller, in 1786, pointed out that they had been too much given to occupy themselves in finding new organisms, he therefore devoted himself to the study of their forms and biological characters, and it was on such data he based a classification. Thus the scientific knowledge gained of these minute bodies was considerably advanced, and the subject now entered upon a new phase: the origin of micro-organisms. It further resolved itself into two rival theories—spontaneous generation, and development from pre-existing germs—the discussion over which lasted more than a century. Indeed, it only ended in 1871, when the originator of the Abiogenesis theory withdrew from the contest, and the more scientific investigations of Pasteur (1861) found general acceptance. This indefatigable worker had been investigating fermentation, and studying the so-called diseases of wines and a contagious disease which was committing ravages among silkworms. Pasteur in time was able to confirm the belief that the “muscadine disease” of silkworms was due to the presence of micro-organisms, discernible only by the microscope. The oval, shining bodies in the moth, worm, and eggs had been previously observed and described by Nägeli and others, but it was reserved for Pasteur to show that when a silkworm whose body contained these organisms was pounded up in a mortar with water, and painted over the leaves of the tree upon which healthy worms were fed, all took the disease and died.
PLATE IX.
AFTER DR CROOKSHANK J. T. Balcomb. del.
TYPICAL FORMS OF BACTERIA, SCHIZOMYCETES, OR FISSION-FUNGI.