Karyokinesis is common not only in inflammatory disturbances, but in new-growths of rapid formation, especially sarcomas, which are formed from mesoblastic cells, the same which have to do with connective tissue. Endothelial cells also undergo the same changes.
The peculiar characteristics of the leukocytes have already been described at considerable length in the preceding chapter. It must suffice, then, here to say that during the inflammatory attack the leukocytes are increased in number, i. e., there is a temporary leukocytosis which is the usual accompaniment of suppuration. For instance, this is regularly present in purulent, but not in catarrhal, forms of appendicitis. The recognition of this fact may be of great value in diagnosis. For instance, leukocytosis is rarely present in tuberculous disease unless suppuration complicates the case. It is met with in suppurative osteomyelitis and in all cases of pocketing of pus. Moreover, when leukocytosis is present coagulability of the blood is increased. Of the various leukocytes, it is the mononuclear and polynuclear forms (see [Chapter II]) which are endowed with the most pronounced activity and which play the principal role among the blood cells or phagocytes. That phagocytosis plays a most important part in the inflammatory process is a matter to be emphasized in more than one way and in more than one place. The account of the process already given should suffice for descriptive purposes; the importance of the act, however, should be made most prominent in considering inflammation and suppuration. That the phagocytic properties of these cells are limited will be remembered when we recall that in certain instances phagocytes, which are incapable of defence as against the mature bacterial organism, are yet capable of englobing the spores and preventing their development. Nevertheless, the activities of even the most lively phagocytes are capable of being influenced and repressed by extremes of heat and cold to which patients may be exposed, either locally or generally.
CHEMOTAXIS AND OPSONINS.
Having considered briefly the cells which take prominent part in the inflammatory process, and the escape along with them of the fluid portions of the blood, whether these coagulate or not, it is necessary before referring to specific factors to discuss that which induces the above cells to act in this way. That there is a peculiar, even a mysterious, attraction which brings specific irritant and phagocyte together has been for some time recognized, but it remained for Pfeffer to study it carefully and to give it the name by which it now passes, i. e., chemotaxis, while others have widened our knowledge of it, especially by a recognition of the opsonins or material which “prepares food,” i. e., prepare microbes for ingestion by the phagocytes.
Chemotaxis is a term implying a peculiar property of attraction and repulsion between cells, both animal and vegetable. It mainly pertains to vegetable cells alone, and has been offered as the explanation of the sporulation of ferns, for example; but as it interests us most in this place it is manifested between the animal cells of the human body and the bacteria, which are vegetable cells. As a result the former, i. e., the phagocytes, having power of migration, are drawn toward the latter. To be more accurate, this mutual or peculiar attraction is known as positive chemotaxis, it being also known that exactly the reverse prevails under certain circumstances, and that mobile cells will move away as rapidly as possible from certain organisms or substances for which they seem to have a repugnance, this being known as negative chemotaxis.
SPECIFIC IRRITANTS.
These are essentially living organisms, bacteria, fungi, and the protozoa, the first named being by far the most frequent. Before a lesion can assume the type of inflammation as here understood some one or more of these organisms must have secured an entrance into the tissues, the circumstances determining such invasion being considered a little farther on. It is these living organisms which, having once invaded the tissues, determine that most active congregation and proliferation of certain cells which we have just described under the head of Phagocytosis. When once the irritants are present there begins that very active conflict which Virchow has so graphically alluded to as the battle of the cells. Now the mysterious chemotactic properties of the component substances manifest themselves, and now phagocyte is drawn toward bacterium, or the reverse, while the tiny war goes on with sometimes varying results, it being a question which can prove victor in the conquest. This is no fiction of the imagination, but is a contest which may be seen under the microscope in certain of the lower animals, while its results may be seen in the examination of pus from any human source. In another place I have also likened this conflict to that in which certain of the enemy resort to poisoned weapons, because modern biological chemistry has now shown very evidently that it is a part of the life history of many of these microörganisms to produce, probably as excretory products, albuminoid or other substances having sometimes extremely toxic properties. And so it comes about that in many of the surgical infections, while the local destruction is produced by the actual death of tissues which have been invaded by microörganisms, the general or systemic symptoms, generally referred to as the toxic symptoms, are literally due to poisons generated in the infected area, dispersed throughout the system, and often proving fatal.
The local effect of these specific irritants, when they are not promptly attacked, devoured, and removed by phagocytes, is pus, which means cellular death, or gangrene, which is death of masses of cells which have not had time to separate from each other. Pus, then, is the ordinary consequence of the contest above alluded to, and each pus cell represents the dead body of a phagocyte which has perished in the attempt to protect the parent organism from harm. That it has died valiantly can almost invariably be determined, because within its dead body may be seen one or more of the minute invaders which it has attacked. This, then, is the light in which inflammation and infection should be viewed.
In other words, we may have escape of fluid portions of the blood, which may or may not coagulate; we may even have some escape of corpuscular elements with some activity in the extravascular cells, which shall lead to temporary or even permanent enlargement of a part; all of which may be provoked by injury or by the presence of certain chemical irritants within the blood or tissues; for example, alcohol, uric acid, etc. But the factors which provoke the greatest activity on the part of intravascular and extravascular cells, and which determine the richness in albumin of fluid exudates, or their prompt coagulation as soon as blood serum has escaped from the vessels, and which particularly determine the furious rush of phagocytes and that kind of intercellular conflict which leads many of the contestants on both sides to death, are living organisms which are introduced from without, whose presence at the point of inflammation is abnormal and injurious, which are offending substances in every respect, while the whole phenomenon of inflammation is an expression of an effort to rid the system thereof. Taking this view of the subject, there is an important distinction between hyperemia and its consequences, which is absolutely a non-infectious condition, and inflammation with its consequences, which is always an infection and is always followed by more or less death of cells, the same being often extruded in a semifluid mass known as pus.