The plants themselves were now washed in distilled water, and the animal products were the semivalve and bivalve shells of which I have preserved many specimens. The semivalve belong to the natural families Buccinum, Lynceus, Helix, and Planorbis; the bivalve to the Cardiacæ. The semivalves are the most abundant. By filtering the water which remained after the shells had been removed, innumerable minute particles like dust were discovered; these particles were ascertained by the aid of the microscope to be mainly composed of minute fragments of aquatic plants and of the spores of fungi; to these must, no doubt, be added, although not visible when dried, the remains of zoophytes, and of the glutinous membranes forming the matrix of animal aquatic life.
I now endeavoured to obtain the glutinous membrane or matrix in which these testaceous mollusca were obviously developed, apart and distinct from the animals themselves. To attain this desirable point we filled a glass receiver with water containing the aquatic plants and shells, and the gelatinous membrane already spoken of. The receiver was now inverted upon a plate, and water poured into the plate to the depth of half an inch.
In a few days the receiver became filled with gas, forcing the water downwards into the plate on which the receiver rested; and although after the first day we could not discover any of the gelatinous membranes in the lower part of the receiver, yet that in the plate became like a flaky jelly, attaching itself to blades of grass or leaves. The surface exposed to the atmosphere became dry and brittle, and in this state resembled thin layers of gum; the substance thus desiccated strongly resembled jelly.
The glutinous membrane of which frequent mention has been made above, is of a very viscid nature, and when combined with any animal substance in a state of transition or fermentation, it is poisonous. It is, I believe, generally viewed as the matrix for the development of the ova of these shell fish, and considered as a product or secretion of the parent. Into this question I enter not, leaving it, if it be one, to others.
On exposing for a few days some of the larger testaceous mollusca alive to the atmosphere of the room at a temperature varying from 65° to 70° Fahr., strong proofs were obtained that ammonia was produced in the interior of the shell confined therein by the membrane called operculum, sealing, as it were, the aperture into the shell hermetically. On puncturing this membrane the presence of ammoniacal gas could be distinctly traced by the odour.
I submit to the consideration of professed physiologists the following questions:—1st. What are the effects likely to result to man from the inhalation of these microscopic and gaseous products in a state of decomposition, they being certainly present in the vapours arising from the waters of canals, ditches, &c., in many countries, especially during the nights of spring, summer, and autumn? 2nd. What are the evil effects likely to arise to man from the use of such waters as drink, or when employed for culinary purposes? Lastly: As the gelatinous membranes alluded to are the nidus of various forms of organic life, and contain those forms, developed and undeveloped, occasionally in a state of decomposition, to which of the two forms of life, animal or vegetable, or to both, is to be ascribed the deleterious effects on man, and ascribed by physicians to an unknown poison called Malaria, designated by them as “a poison, an influence, a miasm, a thing unknown”? Ferments and putrescence are not “things unknown:” let us adhere to facts.
§ 2. Thus the principle of wasting away by the action of the atmosphere, of the rotting of vegetable and animal substances, first developed by the illustrious Liebig, opened up to me the path to that theory which seems to reconcile the conflicting observations of pathologists,—that vegetable and animal matters do ferment or rot, and that in this state of rottenness they are carried through the air, was with me no longer a matter of doubt; next came the question, as to the effects of such matters on man when inhaled by respiration and conveyed directly into the living, circulating blood, that most complex of all fluids, that mysterious compound out of which nature constructs the animal world.
This slow wasting takes place in any damp place under ground, and the ferments assume the form of vapour when such places happen to be warmer than the open air; it is in this state that the odour is so sensible to us after a hot dry day or during cold nights. There is no smell in rainy or damp weather. It is in the spring and autumn months when ferments from slow combustion abound, aided by the amount of heat and moisture which then prevail, and by the floating of plants. The poison thus generated is known to be the product of a ferment, and like many such products, possesses the quality of fermenting other organic compounds with which it may come in contact. Introduced into the living system of man, it finds in certain individuals the material already disposed to pass into fermentation. It incubates, and this incubation is measured as to time by a variety of circumstances I need not enumerate. In cold countries the incubation is slow, extending over many months; not that the ferment differs, but its action is modified by the existing condition of the accessories to its action and power. The ferment introduced into the blood in autumn may not show its full action on the living fluids until the following spring, or early in summer: in hot countries it is different; there the ferment, aided by numerous adjuncts, acts almost immediately; fever sets in, causing violent reaction of the conservative powers of nature; delirium, coma, vomiting, death. The mass of the blood has undergone a change in all its constituents, and dissolution and putrefaction are swift in reducing the frame, even whilst life is still present, to that state to which all that lives must come at last; whilst the physician loses himself in vague theories of an “unknown poison”—a malaria, a something not strictly a gas, a matter or influence differing from all chemical or other agents known, the scientific chemist steps in, and shows that the subtle matter they so anxiously endeavour to discover, is a process constantly going on before their eyes; a chemical process, universal; the process, in short, on which in a great measure depends the disposal of the dead and effete remains of the organic world; the growth, the nourishment, the renovator of each successive generation of the same world.
§ 3. It may be now fully admitted that ammonia is the active principle or stimulus to vegetable life, as shown by the extraordinary growth of plants in warm damp climates; in these malaria—as we may still call the poison so developed—exists to the greatest extent, as in the Pontine Marshes, by the banks of the Po, Ferrara and Bologna. From various experiments and observations, I have been led to the conclusion that the ammonia constantly present in the atmosphere, and derived from several sources,[67] is the chief cause of the activity which the ferment, or poison, displays under different and varying circumstances. There prevails, in truth, an excess of ammonia in such an atmosphere, resulting from the nitrogen uniting with hydrogen; from the decomposition of vegetable matter carrying decayed animal matter along with it; and from the ammonia always existing in the spawn and in the matter of the shells of infusoria. All my researches into the effects which the various gases have upon animal tissues, showed ammonia to be the most destructive; in fact, no animal tissue can resist complete decomposition by caustic ammonia. I conclude, therefore, that vegetable and animal matter in a state of fermentation, and mixed with ammonia, is the cause or essence of that destructive power which physicians ascribe to malaria. Should this fermentable matter pass in a concentrated state into the torrent of the circulation, the globules of the blood are destroyed, and become black; the person is in the cold stage of fever; next, the vegetable matter ferments, causing the hot stage. No one in Holland has any doubt as to the origin of this power, but ascribes it uniformly to the draining of some lake; and it amounts almost to a demonstration that the air under such circumstances is poisonous or injurious to health. It was even foretold by several writers that fevers would result from draining the lake of Haarlem, as took place in the years 1608, 1641, 1727, 1779, from draining various polders.[68]
If the principles I have announced be correct, the extreme impropriety—not to use a stronger phrase—of carrying on excavations or other extensive works on the muddy banks of rivers, in marshy or swampy forests, during the summer months, must be obvious to all reflecting persons. No work should be done in such places, or in ponds, after the month of April, for it is warm dry weather that sets malaria afloat. But if this ferment—which we may strictly call malaria, as producing a malarious condition of the air—be, as I apprehend it is, the cause of fever, why should not medical men direct their attention more earnestly to the question in how far such a fermentation of the blood may be met by the employment of substances known to resist and counteract fermentation? Are physicians agreed on the nature of fevers, and the best means of curing them?[69]