Part 12

The possibility of the occurrence of oedema through nervous influence is not to be denied. The localized and fleeting oedema of urticaria and erythema, the swollen lip and tongue in connection with digestive disturbances, are not to be explained by the two main factors of oedema--viz. venous stagnation and increased permeability of the vascular walls. Cohnheim refers to the rapid occurrence of oedema of the tongue as a result of irritation of the lingual nerve, and oedema is known to occur rapidly in cases of acute myelitis. A similar result follows the experimental destruction of the spinal cord, although the mechanism of its production is not apparent.

Dropsies are subdivided, as regards their distribution, into general and local forms. The causes producing the two varieties are essentially those already described. The causes of all local dropsies are not always to be regarded as the same. Regions which are the seat of mechanical dropsies are often affected by inflammation, with abundant serous exudation--the so-called inflammatory dropsy. The properties of the effusion and exudation are quite different, the former having a small percentage of albumen, but few leucocytes, with a corresponding absence of fibrin, and few or many red blood-corpuscles. The exudation, on the contrary, is highly albuminous, though less so than the blood-plasma; it contains numerous leucocytes and much fibrin; under ordinary circumstances there are but few red blood-corpuscles.

The local dropsies are often characterized by special terms. Hydrops ex vacuo is applied to the collections of fluid found in closed cavities with unyielding walls, as the cranium and thorax, or to the recurrence of fluid in cavities from which the same has been rapidly removed, in the absence of inflammatory disturbances. Collateral oedema is usually applied to the association of oedema with inflammatory disturbances, and represents an extension of the inflammatory process to the region concerned. Oedema of the glottis and circumscribed oedema of the lung are instances. The term hypostatic oedema is often used to designate the association of oedema and inflammation, the former caused by the latter, and to indicate the effect of gravitation in the localization of oedema from the general causes already mentioned.

Another localized oedema of interest, from its frequent occurrence and {72} importance, is oedema of the lungs, often taking place toward the end of life, at times quite suddenly. This form has usually been attributed to increased transudation from arterial congestion or venous stagnation. The former view is directly refuted by the experiments of Welch, who offers the explanation now accepted. With the obliteration of three-fourths of the arterial supply to the lungs of the animals experimented upon, no oedema resulted from the assumed collateral fluxion into the branches of the pulmonary artery which were left open. The obliteration of the same area of venous distribution was necessary before the occurrence of oedema. Oedema of the lungs was further found to result from a ligature of the aorta near the heart. The comparative frequency of oedema of the lungs in man, and the rarity of such extreme mechanical disturbances as those produced experimentally, led Welch to paralyze the left ventricle. The conditions as regards the pulmonary circulation then corresponded with those mentioned as causes for oedema from venous obstruction. The continued action of the right ventricle forced blood into the pulmonary capillaries, where it was compelled to accumulate in consequence of the inability of the left ventricle to receive and expel it. Welch consequently regards the immediate cause of this form of pulmonary oedema as a predominant weakness of the left ventricle. A weak heart does not suffice for the production of the oedema, since this condition is not found when both ventricles are alike enfeebled.

Degenerations.

The degenerations represent disturbances in the nutrition of the tissues of the body, in consequence of which their functions become impaired, if not destroyed. The latter result obviously attends the death of cells, which may occur in the course of the degeneration. The processes concerned are called necrobiotic by Virchow, as they represent vital processes leading to death. Although in many of them the cell is decaying during their continuance, its recovery is possible with the disappearance of the conditions which have transformed physiological into pathological processes. The degenerations affect intercellular substance as well as cells, and are called metamorphoses, infiltrations, or degenerations, as a transformation of normal into abnormal material, or the addition of extraneous substances, or the functional impairment of the part assumes the greatest prominence.

Cloudy Swelling, Albuminoid Infiltration, Granular Degeneration, Parenchymatous Degeneration.

Of the various modifications in the appearance of cells under pathological conditions, there is none, perhaps, more commonly met with than that known by the above terms. A granular appearance may be regarded as an essential characteristic of protoplasm, and is an attribute of cells of epithelial origin as well as of those which belong to other groups of tissues. The abundance of granules present in a normal cell depends largely upon its shape, size, and situation. These granules present various {73} relations to chemical agents, some being soluble in alcohol and ether, others in acids and alkalies, and many of them, especially those met with in the form of degeneration now being considered, show from the various reactions that they are of the nature of albumen. Since their exact composition, in all instances, is undetermined, they are called albuminoid, and when in excess the cell is considered to be infiltrated with these granules, and the organ presents the appearances regarded as characteristic of an albuminoid infiltration. A granular cell becomes much more granular when it is thus infiltrated, and it is therefore a matter of difficulty to recognize from the appearance of certain single cells, as those of the liver or kidney, whether or not the number of granules present is abnormally increased. When, however, a large number of cells of any given organ contain more than the normal quantity of these albuminoid granules, the appearance of the organ becomes modified. In extreme cases the latter is swollen, doughy in consistency, with ill-defined structural details, and in all instances presents an opaque appearance. The term cloudy swelling is thus purely descriptive, and was applied by Virchow to designate the optical appearances of the condition in question. The granules, which disappear on the addition of acids and alkalies, are apparently either added to the cell or result from a precipitation within the same.

Frequently associated with these albuminoid granules are others, distinctly recognizable as globules of fat. An apparent increase of nuclei is often observed, and in certain organs, as the kidneys, the cells seem less coherent than is normally the case. The study of this condition in the kidneys is further of interest as indicating that the border-line between a parenchymatous degeneration and a parenchymatous inflammation is purely arbitrary. From similar exciting causes there may be associated, with the described alterations of the epithelial lining of the tubes, the exudation of albumen, the formation of casts, the desquamation of epithelium, and the presence of leucocytes within the tubules.

When the macroscopic changes are of moderate degree, and the disturbance of function relatively slight, while the concurrent alterations elsewhere, from the simultaneous action of the same cause, are predominant and characteristic of the disease, the condition is conveniently regarded as a degeneration occurring in the course of the latter, rather than an inflammation. The latter term, on the contrary, is to be applied when the granular infiltration of the cells is associated with other evidences of an inflammatory exudation, and when the pathological disturbances are to be directly attributed to the parenchymatous changes.

It is customary to speak of cloudy swelling as a nutritive change, and the condition may be induced by those causes which interfere with the nutrition of parts or of the whole of an organ. Many authorities regard this granular or parenchymatous degeneration as closely allied to fatty degeneration, since many of the causes which produce the one occasion the other. The former is often spoken of as an earlier stage of the latter, from the frequent association of the albuminoid granules with numerous globules of fat as a result of the more prolonged or more intense action of a given cause.

Organs which give evidence of a granular degeneration contain, as a rule, a diminished quantity of blood. This feature is usually attributed to the pressure of the swollen cells upon capillary blood-vessels. The {74} anæmic organ obviously becomes still more cloudy, gray, and opaque in appearance from the diminished quantity or impoverished quality of the blood.

The granular degenerations of the heart, liver, and kidneys, as a whole, usually occur simultaneously, and afford a most important means for the post-mortem recognition of the infective diseases. The condition is therefore to be looked for in the exanthemata, especially in small-pox and scarlet fever, also in erysipelas, septicæmia in its manifold forms, diphtheria, typhoid and typhus fevers, cerebro-spinal meningitis, etc. A common feature in all these cases is the occurrence of fever, and it has been claimed that this element is the cause of the degeneration. In opposition to this view is the well-known fact of its presence in afebrile cases of poisoning from carbonic oxide, and its absence in certain cases of pneumonia and exposure to high temperatures.

The universal occurrence of cloudy swelling in fatal cases of the affections above mentioned leads to the inference of its presence in those instances terminating in recovery without obvious permanent impairment of the organs and tissues concerned. It is therefore agreed that the process may terminate in resolution--i.e. in a disappearance of the excess of granular material. On the other hand, its association, under circumstances, with fatty degeneration suggests as extremely probable that the latter condition may represent a result of the albuminoid infiltration. Even if this more serious issue exists, the possibilities are still at hand for an absorption of the degenerated material and a restitution of the destroyed protoplasm. The effect upon the individual is evidently determined by the persistence and dissemination of the condition, which, in turn, are controlled by the immediate cause and the peculiarities of the individual acted upon.

Fatty Metamorphosis, Fatty Degeneration, and Fatty Infiltration.

The fat which is present within the body under physiological conditions owes its origin primarily to the food taken. A diet which is abundantly fatty furnishes a direct source for much of the fat which appears accumulated in the various organs and tissues. Although it may now appear that such a statement needs but little confirmation, it is not long since the opinion prevailed that nearly all the fat in the body came from the hydrocarbons of the food. This seemed all the more plausible as the herbivora readily accumulated fat, although their diet might contain this element in very small quantities. Hofmann made a decisive experiment with reference to the origin of fat from fatty food by feeding a dog, made lean by starvation, with bacon in abundance, but with little meat. In the course of a few days the greater part of the fat introduced was deposited within the tissues of the animal. Other experimenters have arrived at a similar result, and it can no longer be questioned that fat, accumulated within the body, owes its origin chiefly to the absorption of fat from the food taken.

Another source for the fat of the body has long been suggested--namely, the albuminates of the food. In the admirable article on the formation of fat by Voit, from which most of the information herein {75} presented is derived, it is claimed that he and Pettenkofer were the first to prove the origin of fat in the body, under normal conditions, from albumen. This proof was an inference, however, although presenting a high degree of probability. Valuable evidence in the same direction was furnished by Kemmerich, who found that the milk of a cow during a certain period held more fat than was contained in the food; Subbotin and Voit have shown that more milk is secreted the richer the diet in albumen. Still other observers have furnished more decisive proof that fat is formed from albuminates.

Two sources for fat in the body under physiological conditions are thus recognized: 1, the free fat in the food; 2, the fat derived from the decomposition of the albuminates of the food.

Voit admits the possibility of the hydrocarbons serving as a third source, although this possibility is unnecessary in most cases. Should instances arise, however, where other sources for fat are found insufficient, the hydrocarbons must be regarded as filling the gap.

Fat which is taken into the body is considered to be either consumed or stored. That which is stored is chiefly accumulated in the great reservoirs--viz. the subcutaneous and perinephritic fat tissue, the mesentery, omentum, and bone-marrow--although it may be found elsewhere, in the fluids and tissues of the body. This accumulation serves as a source to be drawn from in case of need, and is called upon where the easily-decomposed soluble albumen is disposed of by the functional activity of the cells. An acting muscle demands food for its work, and consumes first the soluble albumen, then the fat. An excessive waste of fat is delayed by the decomposition of hydrocarbons, but the demands may become so great that albumen, fat, and hydrocarbons are consumed more rapidly and constantly than they can be supplied. It being, therefore, admitted that fat is formed from the albuminates, as well as from the fat of the food, the question readily presents itself whether fat may not be formed from the fixed albuminates of the body, especially from those contained within its cells.

It is well known that in the secretion of sebum the superficial cells of the sebaceous follicles contain fat in great quantity, while the deeper layers are comparatively free from any appearances indicative of the presence of fat. It is further admitted that when pus is retained for a time the individual corpuscles contain fat-drops in quantity and become transformed into fatty granular corpuscles. Eventually, the pus is transformed into a detritus in which fat-drops are found in great number.

Similar appearances may be present in the protoplasm of muscular tissue, the cells of the liver, kidneys, and gastric glands, when poisonous doses of phosphorus or arsenic are given. The occurrence of an acute fatty metamorphosis of the cells of various organs in new-born children has repeatedly been observed. The presence of fat in various organs of the body in pernicious anæmia, and in the heart in connection with stenosis of the coronary artery, is universally recognized. The abuse of alcohol, long-continued obstruction to the flow of venous blood, exposure to high temperatures, are all known to be conditions in connection with which fat-drops are found in the various cells of the body. The effects of poisoning with phosphorus and arsenic are of special importance, as showing that the abundance of fat present in the cells represents a result of the degeneration of these cells, {76} since it takes place when the animal is deprived of food. Although there is an evident destruction of albumen, there is also a diminished elimination of carbonic acid and admission of oxygen. These facts are explicable on the ground that the fat present is not consumed, and the accumulation in the cells is evidence of this lack of consumption. The fat is not simply stored, as none is taken in, nor is any food received from which fat might be formed. Its presence, therefore, must be regarded as due to degeneration.

Since fat may be formed in the body as a result of the metamorphosis of cell-protoplasm, it is desirable to ascertain whether there are any means by which stored fat may be distinguished from that present as the result of a degeneration of the cell. The term fatty infiltration has been used to indicate the presence of stored fat, the latter being regarded as simply taken into the cell and retained for a longer or shorter time, without any necessary interference with other functions possessed by the cell.

In fatty degeneration, on the contrary, it is considered that the quantity of fat present indicates a corresponding diminution in the albuminates of the cell, and is connected with a diminution in the function of the latter, all the greater the more abundant the fat.

It is found that in fatty infiltration, as a rule, the fat is present in large drops, the size of the cell being increased in proportion to the quantity of fat present. Although there may be several drops present, they tend to run together, as is suggested by their different size, varying proximity, and the constant presence of a considerable quantity of protoplasm. In organs, on the contrary, whose function is seriously, even fatally, impaired, the fat, as a rule, assumes rather a granular form. Many minute fat-drops are present, and the cell is not particularly, if at all, increased in size. The more abundant the fat the less the protoplasm. Appearances are met with indicating a transition between cells with few fat-granules and those with many.

If the morphological appearances of fatty infiltration and of fatty degeneration were constant, there would obviously be little or no difficulty in determining the nature of the process manifested by the presence of fat. The exceptions occur both in fatty infiltration and fatty degeneration. In the cells of the liver of an animal poisoned with phosphorus fat makes its appearance in large drops, while in the heart and kidneys of the same animal the fat is present in a granular form.

During absorption from the intestine in the process of digestion fat is present in the epithelium in a finely granular form. When digestion is completed fat is no longer met with in these cells. The presence of large or small drops, therefore, cannot be regarded as a sufficient test of the origin of the fat. It is of equal, if not greater, importance to bear in mind the organ concerned.

In the heart, liver, kidneys, and gastric glands, as well as elsewhere, with the exception, perhaps, of the mammary gland, the presence of many small fat-drops in the cells indicates a degeneration of its protoplasm. The presence of large fat-drops, on the contrary, in the organs and tissues, with the exception of the liver, indicates an infiltration. Large fat-drops, then, may be present in the cells of the liver as the result of an infiltration or of a degeneration. In order to form a satisfactory opinion of the {77} nature of the appearances in the liver in doubtful cases, it is important to note the condition of those organs which may be simultaneously in a state of fatty degeneration.