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INFLUENCES WORKING FOR EVIL UPON THE

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Originally appearing in Volume V20, Page 917 of the 1911 Encyclopedia Britannica.
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INFLUENCES WORKING FOR EVIL UPON THE ORGANISM (I) Malnutrition.—When the See also:

blood See also:supply is entirely cut off from a See also:tissue the tissue See also:dies, and in the See also:act of dying, or after-wards, it suffers certain alterations dependent upon its surroundings. Thus, when the circulation to an See also:external See also:part is obstructed completely, as in the See also:case of a See also:limb where the See also:main artery has been occluded and where the anastomatic communi-cations have not sufficed to continue the supply of blood, the part becomes gangrenous (fig. 24, Pl. II.); that is to say, it dies and falls a See also:prey to the organisms which excite putrefaction, just as would happen to any other dead See also:animal tissue were it unconnected with the See also:body. Fermentative changes are set up in it, characterized by the See also:evolution of See also:gas and the formation of products of suboxidation, some of which, being volatile, See also:account for the characteristic odour. In the formation of these the tissues break down, and in course of See also:time lose their characteristic histological features. The blood suffers first; its pigment is dissolved out and soaks into the surroundings, imparting to them the See also:pink See also:hue so diagnostic of commencing See also:gangrene. Muscle and See also:white fibrous tissue follow next in See also:order, while elastic tissue and See also:bone are the last to show signs of disintegration. The oil separates from the See also:fat-cells and is found lying See also:free, while the sulphuretted See also:hydrogen evolved as one of the products of putrefaction reacts upon the See also:iron of the blood and throws down a precipitate of sulphide of iron, which in course of time imparts to the limb a range of See also:colour commencing in See also:green and terminating in See also:black. The temperature at which the limb is kept, no doubt, favours and hastens the natural See also:process of destruction, so that putrefaction shows itself sooner than would be the case with a dead tissue removed from the body and kept at a See also:lower temperature. Nevertheless, gangrene is nothing more or less than the putrefactive See also:fermentation of an animal tissue still attached to the body. If the amount of liquid contained in the tissue be small in quantity the part mummifies, giving rise to what is known as " dry gangrene." If the dead part be protected from the See also:ingress of putrefactive organisms, however, it separates from that which is living without the See also:ordinary evidences of gangrene, and is then known as an " aseptic See also:slough." Should the portion of tissue deprived of its circulation be contained in an See also:internal See also:organ, as is so often the case where the obstruction in the artery is due to embolism, it becomes converted into what is known as an " infarction." These infarcts are most See also:common in See also:organs provided with a terminal circulation, such as prevails in the See also:kidney and See also:spleen.

The terminal branches of the See also:

arteries supplying these organs are usually described as not anastomosing but many, if not all, of Cohnheim's end-arteries have See also:minute See also:collateral channels; which, however, are usually insufficient to completely compensate for the blocking that may occur in these arteries, therefore, when one of them is obstructed, the See also:area irrigated by it dies from malnutrition. Being protected from the ravages of the organisms which induce putrefaction, however, it does not become gangrenous; it is only where the obstructing See also:agent contains these organisms that a gangrenous slough follows, or, in the case of the contaminating organisms being of a suppurative variety, ends in the formation of a so-called " pyaemic See also:abscess," followed by rapid See also:dissolution of the dead tissue (fig. 24, Pl. II.). In ordinary circumstances, where the artery is obstructed by an agent free from such organismal contamination, the part becomes first red. This is due to intense engorgement of the vessels brought about through these minute existing collateral channels and results in a peripheral congested See also:zone See also:round the infarct. There may be See also:haemorrhage from these vessels into the tissues. This collateral supply not being sufficient to keep up the proper flow of blood through the part the See also:veins tend to become thrombosed, thus increasing the engorgement. The central part of the obstructed area very soon under-goes degenerative changes, and rapidly becomes decolourized. This necrosed area forms the See also:pale infarct. Absorption of this infarcted zone is carried on by means of leucocytes and other phagocytic cells, and by new blood-vessels. If absorption be not See also:complete the See also:mass undergoes caseation and becomes surrounded by a See also:capsule of fibrous tissue—being sharply cut off from the healthy tissue.

Where the malnutrition is the effect of poorness in the quality of the blood, the results are of course more widespread. The muscles suffer at an See also:

early See also:period: they fall off in bulk, and later suffer from fatty degeneration, the See also:heart being probably the first muscle to give way. Indeed, all tissues when under-nourished, either locally as the result of an ischaemia, or generally as from some impairment of the blood, such as that prevailing in pernicious See also:anaemia, tend to suffer from fatty degeneration; and at first sight it seems somewhat remarkable that under-nourished tissues should develop fat in their substance (See also:figs. 26 and 27, Pl. II.). The fatty See also:matter, however, it must be See also:borne in mind, is the expression of dissimilation of the actual substance of the proteids of the tissues, not of the splitting up of proteids or other carbonaceous nourishment supplied to them. A part deprived of its natural See also:nerve-supply sooner or later suffers from the effects of malnutrition. When the trigeminus nerve is divided (Majendie), or when its See also:root is compressed injuriously, say by a tubercular See also:tumour, the cornea begins to show points of ulceration, which, increasing in area, may bring about See also:total disintegration of the eyeball. The earliest See also:interpretation put upon this experiment was that the trophic See also:influence of the nerve having been withdrawn, the tissue failed to nourish itself, and that degeneration ensued as a consequence. The subsequent experiments of Snellen, Senftleben, and, more lately, of See also:Turner, seem to show that if the eyeball be protected from the impingement of See also:foreign particles, an See also:accident to which it is liable owing to its See also:state of See also:anaesthesia, the ulceration may be warded off indefinitely. If the eyeball be kept perfectly clean and no organism be admitted from the outside then ulceration will not follow. If, on the other See also:hand, any pathogenic organisms be See also:present the results are disastrous because the tissue, deprived of its See also:nervous trophic supply, has greatly lessened resistance.

The See also:

bed-sores which follow See also:paralysis of the limbs are often quoted as See also:proof of the See also:direct trophic See also:action of the nerve-supply upon the tissues, yet even here the See also:evidence is somewhat contradictory. Still, there are facts which, for want of a better explanation. we are almost See also:bound to conclude are to be accounted for on the direct nerve-See also:control theory. The common variety of bed-sore is the result of continuous pressure on and irritation of the skin, the vitality and resisting See also:power of which are lowered by a See also:lesion of the See also:cord cutting off the trophic supply to the skin affected. The acute bed-sore is, in some cases, a true trophic lesion occurring, as it may, on parts not subjected to continuous pressure or irritation. Trophic disturbance in the See also:nutrition of the skin may be so See also:great that a slight degree of external pressure or irritation is sufficient to excite even a gangrenous inflammation. Again, a fractured bone in a paralysed limb often fails to unite, while another in the opposite See also:sound limb unites readily, and an ulcerated See also:surface on a paralysed limb shows little healing reaction. A salivary gland degenerates when its nerve-supply is cut off; and the nerves leading up to the symmetrical sloughs in Raynaud's disease have been found in an advanced state of degeneration (Affleck and Wiglesworth). It is just a question, however, whether, even in instances such as these, the nutritional failure may not be explained upon the See also:assumption of withdrawal of the See also:local vasomotor control. There seems to be little doubt, notwithstanding, that one of the See also:chief functions of the nerve See also:cell is that of the See also:propagation of a trophic influence along its axon. When a nerve-See also:trunk is separated from its central connexion, the distal portion falls into a state of fatty degeneration (Wallerian or secondary degeneration). That See also:special trophic nerves, however, exist throughout the body, seems to be a myth. It is much more likely, as Verworn alleges, that the nerves which influence the characteristic See also:function of any tissue regulate thereby the See also:metabolism of the cells in question—in other words, that every nerve serves as a trophic nerve for the tissues it supplies.

It is a significant fact that neoplasms contain very few nerve-See also:

fibres, even although growing luxuriantly, and there is a doubt whether the few twigs contained in them may not merely have been dragged into their midst as the tumour mass See also:expanded (See also:Young). Overwork.—The effect of overwork upon an organ or tissue varies in accordance with (a) the particular organ or tissue concerned, (b) the amount of nourishment conveyed to it, and (c) the power of assimilation possessed by its cells. In the case of muscle, if the available nourishment be sufficient, and if the power of assimilation of the muscle cells remain unimpaired, its bulk increases, that is to say, it becomes hypertrophied. It may be advisable to define exactly what is meant by " See also:hypertrophy," as the See also:term is often used in a loose and insignificant sense. See also:Mere enlargement of an organ does not imply that it is in a state of hypertrophy, for some of the largest organs met with in morbid See also:anatomy are in a See also:condition of extreme See also:atrophy. Some organs are subject to enlargement from deposition within them of a foreign substance (amyloid, fat, &c.). This, it need hardly be said, has nothing to do with hypertrophy. The term hypertrophy is used when the individual tissue elements become bigger to meet the demands of greater functional activity; hyperplasia, if there is an increase in the number of these elements;and pseudo-hypertrophy, when the specific tissue See also:element is largely replaced by another tissue. There are conditions in which we have an abnormal increase in the tissue elements but which strictly should not be defined as hypertrophies, such as new-growths, abnormal enlargements of bones and organs due to syphilis, See also:tuberculosis, osteitis deformans, See also:acromegaly, See also:myxoedema, &c. The enormously See also:long See also:teeth sometimes found in rodents also are not due to hypertrophy, as they are normally endowed with rapid growth to compensate for the See also:constant and rapid See also:attrition which takes See also:place from the opposed teeth. Should one of these teeth be destroyed the opposed one loses its natural means of attrition and becomes a remarkable, curved tusk-like See also:elongation. The nails of the fingers, or the See also:hair of the See also:scalp may grow to an enormous length if not trimmed.

True hypertrophy is commonly found in the hollow See also:

muscular organs such as the heart, See also:bladder and alimentary See also:canal. As any obstruction to the outflow of the contents throws an increased amount of See also:work on the walls, in order to overcome the resistance, the intermittent See also:strain, acting on the muscle cells, stimulates them to enlarge and proliferate, fig. 28, P1. II., and gives rise to adaptive hypertrophy. Should there be much loss of tissue of an organ, the cells of the remaining part will enlarge and undergo an active proliferation (hyperplasia) so that it may be made up to the See also:original amount. Or again, in the case of paired organs, if one be removed by operation, or destroyed by disease, the other at once undertakes to carry on the functions of both. To do so a See also:general enlargement takes place until it may reach the See also:size and See also:weight equal to the original pair. This is known as compensatory hypertrophy. Examples of physiological hypertrophy are found in the ovaries, uterus and mammary glands, where there is an increased functional activity required at the period of gestation. Local hypertrophy may also be due to stimulation resulting from See also:friction or intermittent pressure, as one may see in the thickenings on the skin of the See also:artisan's hands. The extreme development of the muscles in the weight-lifting See also:athlete and in the See also:arm of the blacksmith is the result of increased functional activity with a corresponding increase in the vascular supply; this exercise may produce an over-development so excessive as to be classed as abnormal. In atrophy we have a See also:series of See also:retrograde processes in organs and tissues, which are usually characterized by a progressive diminution in size which may even end in their complete disappearance (fig.

29, Pl. II.). This wasting may be general or local—continuously from the embryonic period there is this natural process of displacement and decay of tissues going on in the growing organism. The functions of the thymus gland begin to cease after the second See also:

year from See also:birth. The gland then slowly shrinks and undergoes absorption. From atrophy of their roots, caused by the pressure of the growing permanent teeth, the " See also:milk teeth " in See also:children become loose and are See also:cast off. The ovaries show atrophic changes after the menopause. In old See also:age there is a natural wearing out of the elements of the various tissues. Their physiological activities gradually fail owing to the constructive processes having become so exhausted from long use that the destructive ones are able to overtake them. As the cell fails and shrinks, so does it become more and more unable to make See also:good the See also:waste due to metabolism. This physiological wasting is termed senile atrophy. General atrophy or emaciation is brought about by the tissues being entirely or partially deprived of nutriment, as in See also:starvation, or in See also:malignant, tubercular, and other diseases of the alimentary See also:system which interfere with the proper ingestion, digestion or absorption of See also:food material.

The toxic actions produced in continued fevers, in certain chronic diseases, and by intestinal parasites largely aid in producing degeneration, emaciation and atrophy. Atrophy may follow See also:

primary See also:arrest of function—disuse atrophy. The loss of an See also:eye will be followed by atrophy of the optic nerve; the tissues in a stump of an amputated limb show atrophic changes; a paralysed Iimb from long disuse shows much wasting; and one finds at great depths of the See also:sea fishes and marine animals, which have almost completely lost the organs of sight, having been cut off for long ages from the stimuli (See also:light) essential for these organs, and so brought into an atrophic condition from disuse. Atrophy may also follow from overwork. Increased work thrown on to a tissue may produce hypertrophy, but, if this excessive function be kept up, atrophy will follow; even the blacksmith's arm breaks down owing to the hypertrophic muscle fibres becoming markedly atrophied. From these causes a certain shrinkage is liable to occur, more evident in some parts of the body than in others. Thus the See also:brain falls off in bulk, and the muscles become attenuated, and in no muscle is this more notable than in the case of the heart. A tendency to pigmentation also develops in certain tissues of the body, such as the nerve and muscle cells. As a result of these various degenerations the functions of the body deteriorate, the faculties become blunted, and the muscular See also:energy of the body is below what it was in earlier See also:life, while the secreting glands in certain instances become functionally obsolescent. Continuous Over-pressure.—The tissues of an animal or plant are all under a certain pressure, caused, in the one case, by the expulsive action of the heart and the See also:restraint of the skin and other elastic tissues, and, in the other case, by the force of the rising See also:sap and the restraint of the periderm or bark. Under this normal amount of pressure they can live and grow. But when-ever, from any cause, the degree of pressure which they are naturally intended to withstand is surpassed, they fail to nourish themselves, become granular, See also:die, and, falling to pieces, are absorbed.

Deleterious Surroundings.—There can be little doubt that all unnatural and artificial modes of life tend to deterioration of the See also:

powers of resistance of the organism to disease. We see it exemplified in plant life in circumstances which are unnatural to the life of the plant, and the prevalence of certain constitutional tendencies among the inhabitants of crowded cities bears evidence to the same See also:law. See also:Man, like other animals, was naturally intended to See also:lead an out-See also:door life. He was originally a See also:hunter and a tiller of the ground, breathing a pure See also:atmosphere, living on a frugal See also:diet, and exercising his muscles. Whenever these conditions are infringed his powers of resistance to disease are lessened, and certain tendencies begin to show themselves, which are generally termed constitutional. Thus the liability to tubercular infection is far commoner in the midst of a depraved See also:population than in one fulfilling the primary See also:laws of nature; See also:rickets is a disease of great cities rather than of rural districts; and syphilis is more disastrous and protracted in its course in the depraved in See also:health than in the robust. See also:Cattle kept within-doors are in a large proportion of cases tubercular, while those leading an outdoor life are much less liable to infection. The improvement which has taken place in the general health of the inhabitants of cities during See also:recent years, concurrent with hygienic legislation, is ample proof of the above assertions. The diminution in the number of deaths from tuberculosis during the last See also:forty to fifty years of the 19th See also:century of itself points in this direction. Every living organism, animal and See also:vegetable, tends to maintain a normal state of health; it is when the natural laws of health are violated that the liability to disease begins to assert itself. If, in these circumstances, the food supply be also insufficient, the See also:combination of influences is sure, in course of time, to bring about a See also:physical deterioration of the See also:race. Certain avocations have a direct and immediate influence in causing diseased states of body.

Thus workers in lead suffer from the effects of this sub-stance as a See also:

poison, those who work in See also:phosphorus are liable to See also:necrosis of bone and fatty degeneration of the blood vessels and organs, and the many occupations in which dust is inhaled (See also:coal-See also:mining, See also:stone-dressing, See also:steel-polishing, &c.; fig. 3o, Pl. III.) are fraught with the greatest danger, owing to the destructive influence exerted upon the lungs by the inhaled particles. Among the most dangerous of the last class (the pneumokonioses) is perhaps that in which the dust particles take the See also:form of finely divided freestone, as in stone-dressing and the dry-polishing on the grindstone of steel. The particles in this case set up a form of fibrosis of the See also:lung, which, either of itself or by rendering the organ liable to tubercular infection, is extremely fatal. The abuse of See also:alcohol may also be mentioned here as a See also:factor in the poduction of disease. See also:Parasitism.—Of all external agents acting for evil, however, probably vegetable and animal micro-organisms with a pathogenic See also:bent are most to be feared. When we consider that tuberculosis, See also:diphtheria, See also:cholera, See also:tetanus, typhoid See also:fever, See also:anthrax, See also:malaria and a See also:host of other contagious diseases have each been proved to be of parasitical origin, an See also:idea may be conveyed of therange of the subject. The living organism may be regarded as constantly engaged in a warfare with these silent and apparently insignificant messengers of destruction and See also:death, with the result that too often the See also:battle ends in favour of the attacking enemy. See also:Heredity.—The tendencies to disease are in great part hereditary. They probably See also:express a variation which may have occurred in a far-back ancestor, or in one more recent, and render the individual vulnerable to the attacks of parasitic See also:fungi, or, it may be, become See also:manifest as errors of metabolism. The psychopathic, the tubercular, the rickety, and the gouty constitution may all be transmitted through a See also:line of ascendants, and only require the necessary exciting agents to render them apparent.

A distinction must be See also:

drawn between the above and diseases, like syphilis and small-pox, in which the contagion of, not the tendency to, the disease is transmitted directly to the foetus in utero.

End of Article: INFLUENCES WORKING FOR EVIL UPON THE

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INFLUENCE (Late Lat. influentia, from influere, to ... 		[next]
INFLUENZA (syn. " grip," la grippe)

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