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and cause stagnation in the movements of the vital liquid. This common derangement in the blood is continually observed by the employment of the microscope. It can, indeed, be artificially brought about at any time in the transparent membrane of the frog's foot, where it can be watched in its progress. What is termed inflammation, in whatever form, is in the first instance simply over-abundant generation and deposit of agglomerations of bioplasm, and the consequent stagnation and arrest of the blood-flow through the capillary extensions of the vessels. As the stagnation in the affected part becomes more decided and more pronounced, the heart augments the force of its stroke in its endeavour to overcome the abnormal resistance, and under this increase of injecting force the fine walls of the delicate vessels yield, so that their internal channels become enlarged and dilated. In cases of extreme mischief they even give way, and the rapidly growing aggregations of clotted bioplasm gather outside and around the proper channels of the blood-flow as well as within them. There is then swelling in the affected part, in consequence of the stagnation and unnatural engorge
, ment; and there is pain, in consequence of the way in which the unnatural aggregations and engorgements press upon the
There is also increased heat, or burning (inflammatio), which for a long time was conceived to be actual combustion of the texture of the part under the influence of more rapid oxidation, but which is now known to be something very different. In all derangements of this character there is less, rather than more, oxydation and reduction of the complex principles of the textures of the body. The excessive heat is really due to the over-abundant and too rapid formation of aggregations of plastic bioplasm. When the less elaborated material of blood is converted into life-plasm heat is set free, which was previously operative as latent force in holding together its constituents. The movement of the blood having become either sluggish or stagnant, the abnormally increased supply of heat is not carried away, but remains accumulating in the part and giving rise to the burning' temperature which provides the derangement with a name.
A similar condition of too rapid increase of bioplasm, and too lingering motion of the blood-streams, with a tendency to stagnation in the capillary channels of the circulation, when it occurs everywhere throughout the body, instead of being confined to one particular organ, or narrow spot, constitutes the disorder which is known as “ fever.' In ordinary fevers the derangement is brought about mainly by mere incidental depravity in the formation of the blood ; too much of certain
adhesive and plastic principles are thrown into it from the food, and too little of certain effete and contaminating principles are removed from it by the agency of the red blood-corpuscles and of the various organs of elimination, such as the lungs, the liver, and the kidneys, which are properly the scavenger department of the animal economy. But in infectious fevers' the same depraved and disordered condition is set up in individuals who would not otherwise have experienced it, by their having been incidentally placed under the infecting influence of blood already affected by this kind of contamination. What, then, is the precise mode, and effective cause, of the communication of the disorder from the blood of the affected individual to that of the previously unaffected one? Do the researches of the physiologist into the nature of blood-constitution, and life-plasm, throw any material light upon this important consideration ?
In the first place, physiological science does show that, in the vaccine lymph, which reproduces the vaccine form of variolar disease when introduced into previously healthy blood, a myriad of minute aggregations of living matter, obviously of very similar nature to corpuscular aggregations of bioplasm, are rapidly produced, and that the power of the lymph to communicate the disease is almost certainly due to these minute aggregations. If they are removed from the lymph by filtering it, the remaining liquid part is found to have lost entirely its vaccinating power; and, on the other hand, the aggregations left when the lymph is filtered away are potent as vaccinating agents, and continue to be so even when they have been approximately dried, and kept in that state for days and even weeks, provided they are replaced in the substance of warm living blood. These corpuscles of vaccine lymph have now been again and again examined by microscopic object-glasses that magnify them some 5,000 diameters, and with these high powers they look marvellously like white blood-corpuscles and exhibit the same inherent power of vital movement that has been described as belonging to those little bodies. There is, therefore, in this instance, actual demonstration of the production in the blood of visible and tangible disease-germs, capable of reproducing specific diseased action in other blood, and which are, to all appearance, living bodies in the sense in which blood-corpuscles are so.
And again, physiological science has been able amply to demonstrate that when mere simple and incidental inflammatory derangement is produced in a living body, some of the plastic material, which goes in more favourable and normal conditions
to constitute healthy texture, takes to producing little aggregations of life-plasm, which have thenceforth lost all power of performing constructive work in the system, but are able to reproduce generation after generation of other like aggregations, even after they have been removed to liquids not originally forming part of the organisation from which they are derived ; and, what is of further importance to the argument, physiological science can show also that almost every kind of texture of which the organised structures of the living body is composed, is capable of having its vital energy diverted from the ordinary work of generating vesicles required for constructive purposes, to the extraordinary work of producing these rapidly-multiplying aggregations of bioplasm. The little bodies which are thus produced are what are termed 5
pus* corpuscles.' They are the indispensable base of what is known as purulent matter. When these products of disease, the puscorpuscles, were first detected and observed, they were described as little vesicular' bodies of a spherical shape, surrounded by a filmy investment or cell-coat, and containing within the cell-wall granular substance. It is now, however, well known that the pus-corpuscles most ordinarily seen are merely the dead débris of the living and active pus-corpuscle. They are aggregations of granules, and of oil-globules resulting from the disintegration and destruction of living matter and enclosed in a kind of cerement of coagulated albumen that has formed around them. The actually living pus-corpuscle is, like the colourless blood-corpuscle, devoid of all vesicular investment, and a mere naked mass, or aggregation, of lifeplasm. But it is an aggregation in which a notable change has been brought about. It is bioplasm which has lost its constructive capacity and energy, and which has acquired in its place a remarkable increase of a lower reproductive power. The constructive force which, in ordinary circumstances, is directed to the development of cells and to structural achievement, is turned to the generating of a countless myriad of incoherent and, so to speak, degraded though still living spherules.
It may perhaps be well to remark, in passing, that the object of the conversion of true bioplasm into the pus-globule is a beneficent one. It is principally by means of this degradation of the ordinary state that the hurtful stagnations and coagulations of inflammatory disorders are removed. Masses of adhesive bioplasm, that have clogged some important track of texture and plugged the channels of the blood-stream, are changed into loose and unadherent pus-corpuscles, which are
easily scattered and removed out of the way in consequence of their incoherency.
It is therefore, in this case, clear that the actual substance of the textures of the living frame can be changed into a degraded form of existence in which, although the proper powers of constructive activity are lost, a lower kind of vital activity is still retained. Now the most recent and perhaps, upon the whole, the most reasonable notion of the nature of the propagation-germs of infectious diseases is that they are in all the essential particulars of the same character as vaccine and pus-corpuscles; minute aggregations of life-plasm, primarily derived from the perversion of ordinary and healthy bioplasm, and transformed into a new state of vital existence in which restless impulse in self-reproduction takes the place of proper constructive work; where the same kind of action that is so beneficently brought into play for a reparative and remedial end in the case of the pus-corpuscle and purulent matter runs riot, and is enlisted in the work of destruction and death.
There is no difficulty whatever in understanding how diseasegerms of this character can become the potential cause of the communication of specific disease, and can find their way from the interior of one living creature into the interior of others of like organisation. The inlets and outlets through which bodies of even such fineness as the corpuscular aggregations that have been actually seen by the microscope could pass, are practically infinite in number. Dr. Beale states that he has, in favourable circumstances when working with the fiftieth of an inch focus object-glass, distinctly seen corpuscular aggregations in pus with dimensions not exceeding in breadth the hundred thousandth part of an inch, presenting all the distinctive characters of bioplastic life, and throwing off continually subordinate spherules and corpuscular germs that were just, even with those advanced powers of the microscope, upon the margin of invisibility. Even the largest of these aggregations would have scarcely a fiftieth part of the breadth of the blood-corpuscle, and would float about in currents of air, a thousandfold more readily than the minute particles of dust that are carried by the same agency to every nook and cranny of dwelling-houses to be deposited there in constantly accumulating heaps. Dr. Beale, in pursuing the line of thought suggested by the observation of these minute objects, very strikingly remarks that there are most probably living creatures of such exquisite tenuity that they can actually climb, without muscles or limbs, not only through fluids, but even upon the
particles of air itself. Disease-germs, of even such tenuity as appear to have been traced in the researches of Dr. Beale, would ride with the utmost facility in the interior of the bloodcorpuscles. One colourless blood-corpuscle could accommodate thousands of the pigmies in its comparatively vast sphere. Such disease-germs would be easily poured through the actual films of the ultimate capillary vessels of the blood-channels into surrounding textures, and also into open and external airfilled
space, almost as freely as if they were not imprisoned in any way.
The capability of infectious disease to be communicated from an affected to a previously unaffected frame, by the direct passage
of material substance from one to the other, is an affair of actual demonstration when the matter of the vaccine pustule, or of the pustule of small-pox, is taken upon the point of a lancet and passed by it through a puncture of the skin into the blood of a vaccinated, or innoculated, person. It is almost as manifest that cholera contagion can be introduced by the use, as a drink, of water containing the excreta of persons who have suffered from choleraic disease. The proof has been made quite as complete in the case of contaminated air by German physiologists, for they have been at the pains to communicate small-pox to sheep by making them breathe through a shirt that had been worn for twelve hours by a man ill with smallpox.
Very commonly a relaxed and weakened condition of the fine vessels of the organised textures, and a lowered power of healthy resistance, are coincident with just that depraved condition of the blood which inclines to congestion and stagnation in the capillary channels of the circulation, and to ready transudation through their walls. In such morbidly disposed blood there is nearly always a deficiency of coloured corpuscles, and consequently a defective fulfilment of the reducing and oxydising processes which are so necessary to the maintenance of blood at the proper standard of health. In all feverish diseases constituents of the blood, which under the more favourable circumstances of perfect health are rapidly oxydised and thrown out from the system through the eliminating outlets of the lungs, kidneys, digestive canal and skin, are retained in the channels of the circulation unoxydised, or are painfully and imperfectly removed from it in a too partially reduced and oxydised state. It is now clearly understood that in every form of grave disease there is a preparation for the outbreak of the more advanced and palpable phase of the disorder, through the slow, gradual, and insidious derangement of the condition of