Part 7

The liquid portion of the exudation represents something more than the transuded blood-serum, and a certain practical importance results from the distinction drawn between an exudation and a transudation. Such a distinction is especially called for when the inflammatory or non-inflammatory origin of considerable quantities of fluid in the larger cavities of the body is concerned. From a recent contribution to our knowledge of this subject by Reuss the following information is derived: The percentage of albumen is always greater in exudations than in transudations, and is more constant in the former than in the latter. It increases with the severity of the inflammation, being highest in the ichorous forms, less in the purulent, and least in the serous exudations. When an {43} inflammatory exudation is found to contain less albumen than usual, the existence of a transudation with secondary inflammation is suggested, or the exudation may have taken place in a hydræmic individual. A sufficient number of exceptions are met with, however, to interfere with the absolute nature of this test.

The coagulation of an inflammatory exudation apparently depends upon the contained white blood-corpuscles; the more numerous (within certain limits) these are in a serous exudation, the more abundant is the formation of fibrin. The cellular element likewise is that which in abundant liquid exudations characterizes them as purulent. Although it is generally agreed that most of the corpuscles of pus are emigrated white blood-corpuscles, it is not necessary to admit that all are of this nature. The cells present in an inflamed part include those pre-existing, as well as those which escape from the vessels. The former are the wandering cells of the connective tissues, as well as the fixed variety, the epithelial cells of the surface of a mucous membrane in addition to the subjacent connective-tissue cells. Amoeboid cells outside the blood-vessels have been seen to divide, and it is possible that such duplication may serve as the method of formation of a certain number of pus-corpuscles. The statements concerning the proliferation of the fixed connective-tissue cells and of epithelium are derived from appearances, and are interpretations of these appearances, not observations of a process.

The changes taking place along the walls of the blood-vessels being the feature of prime importance in the observation of the progress of an inflammation, numerous investigators have directed their attention to the determination of the nature of the changes in the vessel wall by means of which the escape of the corpuscles is permitted. Arnold represents the most strenuous advocates of the stomata theory, according to which the leucocytes pass through canals normally existing in the wall. By means of the silver method of staining, and by injections of various insoluble pigments into the blood-current, certain results are met with, which give color to the view that pores and canals are present upon and in the walls of the vessels, analogous to those found in the diaphragm. As the latter have been shown to be in direct communication with the lymphatic system of tubes and spaces, so the walls of the blood-vessels have been assumed to present similar channels of communication.

The prevailing views at the present time are in favor of the artificial nature of the stomata and pores in the walls of the blood-vessels. An increased porosity of the vascular wall in inflammation is necessary for the occurrence of the exudation, but such porosity is regarded rather as a physical condition permitting an observable filtration, and a filtration of solids as well as liquids.

In this connection reference should be made to the observation of Winiwarter, who has demonstrated that colloid material, a solution of gelatin, passes through the vascular wall in inflammation more readily--i.e. under less pressure--than through the normal wall of the blood-vessel.

The causes of inflammation are to be regarded as those which produce an increased porosity of the vessel wall without causing its death, for no exudation escapes from a dead vessel, its contents becoming clotted.

These causes may act from without or from within, primarily affecting {44} the tissues outside the vessels, or exerting their action, at the outset, upon the wall itself. The usual histological relation of vessels and surrounding tissues is such that both are simultaneously affected. The occurrence of an inflammation in non-vascular parts, however, as the cornea, from irritation of its centre, the part farthest removed from the surrounding blood-vessels, shows that the affection of the vessels may be indirect as well as direct. This indirect action is to be regarded as taking place through the agency of nerves or through that of the nutritive currents. That nervous influence alone does not suffice to transmit the effect of an applied cause is apparent from the absence of inflammation of the cornea which has become anæsthetized by section of the trigeminus nerve. With the protection of the cornea from external irritation there is an absence of inflammation.

The consideration of the final symptom of inflammation, the disturbance of function, which has been added in recent times, belongs to special rather than general pathology. It varies according to the seat of the inflammation, the disturbed function of the brain or heart differing from that of the liver or kidney. The clinical importance of this symptom of inflammation is greater than of all the rest, as it is the one whose presence is constant and indispensable.

An inflammation may exist, as already stated, without heat, redness, or pain. The swelling may escape observation from the limited quantity of the exudation and other causative agents, or from the inaccessibility of the inflamed part to physical examination. The disturbance of function, however, becomes early apparent, and is present throughout the course of the inflammation. A knowledge of its nature enables the seat of the latter to be recognized, and its variations furnish a desired test of the efficiency of therapeutic agents.

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The causes of inflammation may be divided into the traumatic, toxic, parasitic, infectious, dyscrasic or constitutional, and trophic.

The traumatic causes are those which act mechanically, producing an injury to tissues by pressure, crushing, tearing, stretching, and the like. Others represent modifications in temperature, thermic agencies, and include extremes of cold as well as of heat. The chemicals whose action is direct, as caustic, include a third variety of the traumatic causes. Such chemicals are applied to surfaces, cutaneous or mucous, and comprise the active element producing the perforating ulcer of the stomach and duodenum, as well as such substances as potash or sulphuric acid which may have been swallowed intentionally or accidentally.

The toxic group of causes is closely allied to the chemical variety of the traumatic agencies. It includes chemicals whose action is indirect, through absorption in a diluted form rather than from direct application in a concentrated condition. Such chemicals are derived from without, as arsenic, phosphorus, and antimony; or may be formed within the body, and the latter include the chemical products of putrefactive changes--in the urine, for instance--and, with considerable probability, certain of the active agents of blood-poisoning in septic diseases. It is not unlikely that some of the inflammatory affections met with among the so-called constitutional diseases, as rheumatism and gout, may owe their origin to the production of chemical substances within the body, excessive in quantity if not changed in quality.

{45} The parasitic causes of inflammation are both animal and vegetable, and act upon the surfaces of the body or within its deeply-seated parts. Some of the animal parasites act locally at their place of entrance, while others produce but slight disturbances in this region, their effects usually resulting from the transfer of their offspring to remote parts of the body. The vegetable parasites are for the most part the various fungi, which act locally upon the skin or on those transitional surfaces lying between skin and mucous membrane. The resulting parasitic inflammations are known as favus, sycosis, ringworm, thrush, etc. The border-line between such parasitic diseases and those included among the infective diseases is somewhat arbitrarily drawn. Parasites in the limited sense act chiefly as foreign bodies, while the effect of minute vegetable organisms is rather that of ferments, in virtue of their products. Such a distinction is of relative value merely, as the micrococci and bacteria are capable of acting in other ways than by the production of septic material.

The infectious causes of inflammation are for the most part parasitic in their nature, although the discovery and identification of the parasite are in most of these inflammations assumed rather than demonstrated. The relation of the anthrax bacillus to malignant pustule no longer admits of a doubt, mainly in consequence of the researches of Koch. This investigator has been enabled to establish a definite etiological relation between the septicæmia of certain animals and accompanying minute vegetable organisms. His recent discovery of the bacillus of tuberculosis definitely removes the tubercular process from the group of dyscrasic or constitutional affections to that of the infective diseases. The constant presence of minute organisms in relapsing fever, leprosy, malaria, typhoid fever, diphtheria, erysipelas, and numerous other affections associated with, if not characterized by, inflammatory conditions, renders extremely probable the closest pathological relation between such diseases and a microscopic organism. That an inflammatory process may be regarded of infectious origin, it is necessary, according to Koch, that a characteristic organism should be found in all cases of the disease, and in such numbers and distribution as to account for all the phenomena of the disease in question.

These organisms may act in virtue of their growth and the consequent demand for oxygen, as seems probable in certain cases of malignant pustule, where the affected individual dies with symptoms of asphyxia. Their operation may also be like that of ferments, which produce chemical material whose effect may be remote from the immediate presence of the minute organism. They may likewise, in connection with their colonization in various parts of the body, act more immediately upon the walls of the blood-vessels, and produce that increased porosity which is so essential a factor in inflammation.

The discovery of the immediate cause of the various infective diseases, as measles, scarlatina, variola, cholera, dysentery, mumps, whooping cough, cerebro-spinal meningitis, and numerous other epidemic and endemic affections, still remains a question for the future. The constant association of microbia with any or all of such diseases is but one fact in connection with them, and such a discovery is to be regarded merely as a step forward, to be followed by others, each of which represents not only an advance, but confirms the position attained.

{46} The dyscrasic or constitutional causes of inflammation are those which, though long established, appear less demanded as our knowledge advances. Regarded as the result of an alteration in the composition of the blood, it is obvious that such changes may arise from the introduction, from without, of wholly foreign material. The dyscrasia may also represent modifications in the relative proportion of the normal constituents of the blood. In the former series are included what, for the most part, have already been referred to under the toxic and infectious causes of inflammation. The dyscrasiæ from lead, alcohol, and the like belong to this series. Still more important are the poisons, the virus of tuberculosis and scrofula, of leprosy and syphilis. The dyscrasiæ known as anæmia, leucæmia, uræmia, icterus, and diabetes are to be regarded less as inflammatory causes than as predisposing conditions which favor the action of other groups of causes.

The trophic causes of inflammation are those whose action is supposed to take place through the influence of nerves. Although, as has already been stated, a faulty innervation of tissues is an important element in favoring the action of various inflammatory causes, there remain certain forms of inflammation where the disturbance of nervous action seems to be the essential feature. The occurrence of an acute peripheral gangrene soon after certain traumatic or inflammatory lesions of the brain or spinal cord, of articular inflammation following chronic affections of the cerebro-spinal axis, are instances in point. The origin and distribution of herpes zoster, the occurrence of sympathetic ophthalmia and symmetrical gangrene, suggest a predominant disturbance of innervation as the exciting cause. At the same time, it is desirable to call attention to the recent observations of MacGillavray, Leber, and others, which suggest that a sympathetic ophthalmia is due to the extension of a septic choroiditis along the lymph-spaces of the optic nerve. It is further apparent that in certain so-called trophic inflammations, as the pneumonia after section of the pneumogastric, and the inflammation of the eye following paralysis of the trigeminus, the paralysis of the nerve is a remote, rather than an immediate cause, of the inflammation. There still remain, however, a number of localized inflammations whose origin is so intimately connected with nervous disturbances as to demand, for the present at least, a corresponding classification.

The course of an inflammation is often indicated by the predominance of certain symptoms, which, for the most part, indicate a condition of the individual acted upon rather than a peculiarity of the cause. The sthenic inflammations take place in robust individuals with powerful hearts and an abundant supply of blood. In such persons a strong pulse, high fever, and an injection of the superficial blood-vessels suggested, in former times, the necessity of bloodletting as the essential therapeutic agent. The sthenic form of inflammation was most commonly associated with pneumonia, where the obstruction to the passage of blood through the lungs was an important cause of the superficial injection of the blood-vessels.

The asthenic inflammations, on the contrary, are those occurring in feeble individuals, debilitated in consequence of pre-existing disease, exposure, or habits. A weak heart, low febrile temperature, and {47} superficial pallor, characterize the asthenic inflammations, which show a frequent tendency to become localized in the more dependent parts of the body, the force of the circulation being too feeble to overcome the effect of gravitation.

In the typhoidal inflammations are associated those symptoms which are so prominent in the severe varieties of typhoid fever. These are the predominant symptoms: hebetude or low, muttering delirium, picking at the bed-clothes, involuntary evacuations, stertor, and the like. The nervous disturbances are associated with a feeble pulse and a dusky hue of the skin.

The constituents of an inflammatory exudation are frequently used as a basis of classification, and characterize the inflammation from the anatomical point of view. As the exudation is complex in its composition, the predominant element is made use of to designate the variety, and in doubtful cases a combined adjective indicates the presence of the two most abundant constituents. As the exudation is directly derived from the blood and contains serum in addition to white and red corpuscles, the serous, purulent, and hemorrhagic varieties of exudation naturally arise. The fibrinous and diphtheritic inflammations relate to the presence of membranes or false membranes. Finally, there are the productive inflammations, resulting in the new formation of tissue, and the destructive inflammations, where losses of substance occur.

Serous inflammations are most frequent in those parts of the body where the structure contains the largest lymph-spaces. The so-called serous cavities of the body offer the most favorable opportunities for the accumulation, as well as for the exudation, of the inflammatory product; then follow the regions of the larger lymph-spaces, according to the size and number of the latter.

The serous inflammations may also arise from the epithelial coverings of the body, as the cutaneous, alimentary, and respiratory surfaces. The serous exudations of the skin are those present in vesicles, blisters, or bullæ, which owe their limitation to the resistance offered to the spreading of the liquid inflammatory product by the coherent epidermis. Serous inflammations of the alimentary canal may assume a vesicular character, although, from the structure of its mucous membrane and the macerating influence of its contents, the vesicles are apt to be of an extremely transitory character.

The more important serous inflammations of the intestines are those manifested by profuse watery evacuations, the extreme form of which is to be found in cholera.

Serous inflammation of the lungs accompanies the more severe forms, and usually represents but a limited and circumscribed affection, associated with more abundant cellular and fibrinous products.

Serous inflammations of the peritoneum, pleura, pericardium, tunica vaginalis, and central ventricles often give rise to the presence of enormous quantities of fluid, whose partial removal from many of the cavities concerned by operative measures frequently represents a most beneficial result of treatment.