ON THE DECOMPOSITION AND METAMORPHOSIS OF ANIMAL BEINGS, AND ON THE INFLUENCE THEY EXERCISE OVER THE SOIL AS A HABITAT FOR MAN.  
During life animal bodies undergo continual decomposition and recomposition; life is in fact a perpetual metamorphosis. Whilst alive, the products of vitality (excreta) are returned to or deposited in or on the surface of the earth, and carried by drainage and other means into the nearest water, river, or stream; we have lived to see them thrown en masse into a tidal river the waters of which serve at the same time to furnish most of that required for the economy of a vast capital and many surrounding towns; in the same country the cesspools and dead-wells constructed to receive the liquid and solid excreta of dwelling-houses are not unfrequently constructed close to the pump-well which is to supply the inhabitants with pure water for culinary purposes.
To these extraordinary facts I shall shortly return. They show the extent to which intelligent, talented, shrewd men may suffer themselves to be deluded and led aside from the path pointed out by common sense, more especially when crotchets are substituted for principles; when men fancy that in following out some imperfectly-observed inquiry, they are imitating nature —that nature which is ever consonant with herself, which created all animals, and which knows how to dispose of their excreta when living, and of their remains when dead, without detriment to the living. The Caffre, the Hottentot, the Bosjieman, the North-American Indian, the Bedouin, require no sanitary arrangements, no laws regulating, nor staff to carry out a code of theoretical Utopian schemes, sure to revert on the heads of those foolish enough to employ them; the excreta deposited on the earth disappear, so do also the remains of animal life. We never hear of any pestilence, fever, scurvy, dysentery, small-pox, hooping-cough, malignant sore-throat, or other zymotics, originating amongst them. It would, indeed, almost seem that such evils do actually owe their origin to human agency and to human civilization; where civilized man makes his highest endeavours, there his most signal failure occurs; experience teaches him nothing; the insolence of wealth naturally leads to the contempt of all knowledge derived from means otherwise than national and native. In Britain the muddy banks of rivers, which in Holland and Belgium are covered with vegetation, lie exposed, festering in the sun’s rays, the fertile source of agues and other diseases; here they are being continually exposed, or alternately covered with water, which is then allowed to evaporate; this mud is not suffered to rest, but stirred up in a variety of ways, as best suits the convenience of the parties interested. It suits, for example, the proprietor of a long-neglected drain or sewer, cesspool or filthy stagnant canal, or a common ditch, which once was a clear rivulet, to cleanse it out. He selects the warmest weather and the longest day for that special work, or he spreads the contents of the cesspools of half a century’s collection on the fields, suffering it to remain there for weeks, thus rendering the roads all but impassable. The selected lives of the finest men in the kingdom, petted, fed, clothed, and lodged at the public charge, without anxiety or a care for to-morrow—the Guards of England—die under his fostering hand, in the ratio of three to one of the care-worn and toil-exhausted peasant, miserably fed, scantily clothed, badly lodged, and full of anxiety for the morrow. Now, how comes this? Simply, I believe, from this—that man, knowing much better than nature, has chosen to take her place, to do her work clumsily, and to fancy that he is doing it well; to interfere, and not to carry through the works he has undertaken. What other proof can be required than the fact that, on the frontiers of the Cape of Good Hope, in the healthiest country in the world—a fact proved not only by the statistics of the celebrated statistician, Major Tulloch, but by the evidence of all medical men who have resided there,—where the mortality is not a half of what it is amongst the most favoured counties of England—in such a country, where every man might have had a mile square of ground to live on, military arrangements contrived to break down whole regiments of the healthiest young men England could produce.29
The Dutch Boers and Hottentots were astonished, as well they might be. “Towards the end of June, 1836,” observes Major Tulloch, “very decided symptoms of scurvy began to manifest themselves among part of the 75th Regiment at Fort Armstrong, and subsequently extended to most of the other stations along the frontier. The total number of cases reported either as scorbutus or purpura, were 134, of which 4 proved fatal; the others readily yielded to change of air, with improved diet and accommodation.” As was to be expected, the Hottentot troops, on the same ground, being left to act generally in accordance with the dictates of their own common sense, wholly escaped the disease.
Let us now briefly review the means adopted by nature for the disposal of those remains so embarrassing to the civilized, so innocuous to man living in a semi-barbarous or savage state, and which prove to the former a source of infinite expense, discomfort, and disease. The problem has reference to the soil, to the air, to the water; to the condition of all three as regards the preservation of animal life generally, man included.
I have already remarked in a preceding chapter, that all organized beings after death undergo a change, in consequence of which their bodies, as such, disappear from the surface of the earth. In a short time after the event, animal matters lose their cohesion; they are dissipated into the air, leaving only the mineral elements they had derived from the soil. The change commences immediately after death: with the aid of moisture and exposure to the air, the bodies of animals, as well as plants, undergo changes, the last of which are30 the conversion of their carbonic acid and of their hydrogen into water, of their nitrogen into ammonia, of their sulphur into sulphuric acid. Thus, their elements assume or resume forms in which they can again serve as food to a new generation of plants and animals. “The same atom of carbon which, as the constituent of a muscular fibre in the heart of a man, assists to propel the blood through his frame, was perhaps a constituent of the heart of one of his ancestors, and any atom of nitrogen in our brain has perhaps been a part of the brain of an Egyptian or of a negro.
“As the intellect of the men of this generation draws the food required for its development and cultivation from the products of the intellectual activity of former times, so may the constituents or elements of the bodies of a former generation pass into, and become parts of, our own frames. The proximate cause of the changes which occur in organized bodies after death is the action of the oxygen of the air on many of their constituents. This action only takes place when water—that is, moisture—is present, and requires a certain temperature.”
The great agent in all these changes is oxygen, as has been already sufficiently explained when speaking of the decomposition of vegetables after death. I shall first attend to the influence these changes have on the soil as producing agents, intended to restore to the soil those vivifying powers which it never seems to lose when man interferes not; and lastly, to consider briefly its influence on man himself.
The development of scarcely any plant can be imagined without the assistance of nitrogen or of azotized materials. Now, under certain conditions known to all botanists, this azote must come from rain water, either in the form of atmospheric air, or under that of ammonia. Chemists have, I think, proved that it originates in the ammonia contained in the atmosphere, and not in the azote as it naturally exists in the air. The problem is put and solved in this way by Liebig, “Let us consider a farm suitably conducted, and of an extent sufficient to maintain itself, ammonia exists there in a sufficient abundance in rain water and snow; in the water of most fountains; it exists in the air in abundance, and is being constantly renewed by the decomposition of animal and vegetable bodies, and is restored to the soil by the rain, and then absorbed by the roots of plants, and produces, according to the organs, albumen, gluten, quinine, morphine, cyanogene, and a great number of other crystallized combinations.”
The most decisive proof of the part played by ammonia in the nourishment of plants is furnished us by the use of manure in the cultivation of cereals an............