ANÆMIA.
A reduction in the amount of the blood or of its corpuscles occurs under a great variety of circumstances. Broadly speaking, we can recognize two great clinical and pathological groups of cases: I. Those induced by causes acting upon the blood itself; and, II. Those induced by disturbance in the functions of the blood-making organs.
I. Of causes acting directly upon the blood, we shall consider—
1st. Hemorrhage, traumatic or spontaneous. A high grade of anæmia may be quickly produced by loss of a large quantity of blood, and the reduction is in all the constituents; there is a true oligæmia. If the amount lost be excessive, death results from the diminution in the total volume of blood and general lowering of the arterial pressure. If the hemorrhage is sudden and profuse, as from a large vessel, the loss of four or five pounds of blood, or even less, may be sufficient to induce fatal syncope. In hemorrhage into the pleura or peritoneum from rupture of aneurisms, etc., it is rare to meet with more than three or four pounds of clot and serum; seven and a half pounds is the largest amount I know of shed into one of the cavities (pleura) by rupture of an aneurism. When the bleeding extends over several days, the amount lost may be very much greater. In cases of hæmophilia extraordinary accounts are given of the amount collected in the course of a few days. In a case of hæmoptysis a patient lost over ten pounds by measurement in one week, and then recovered from the immediate effects. After the most severe hemorrhages the reduction in the number of red corpuscles is not nearly so great as in forms of idiopathic anæmia. Thus in the case just mentioned at the termination of the week of bleeding there were 1,390,000 red corpuscles to the cubic millimeter. In any single bleeding a fatal result follows the loss of one-third or one-half of the total blood-volume. The process of regeneration of the blood goes on with astonishing rapidity, and in some bleeders a week or ten days will suffice to re-establish the normal amount. The restitution begins even during a hemorrhage by the absorption of lymph from the tissues under the lowered pressure in the vessels. The dryness and stickiness of the serous membranes after death from a profuse hemorrhage is usually very marked. The water and saline constituents of the blood are readily restored by absorption from the gastro-intestinal tract. The albuminous elements are also quickly renewed, but it may take weeks or months before the number of corpuscles reaches the normal standard. Indeed, this condition of oligocythæmia, as it is called, may persist, grow worse, and ultimately prove fatal. The microscopical characters of the blood after severe hemorrhage are not much changed, except as regards the white corpuscles, which are relatively increased, and the fibrin network, which is much less marked than in health. The white corpuscles may be very slightly reduced in number per cubic millimeter—a fact to be accounted for either by a relatively diminished loss during the bleeding, owing to their adhesiveness and wall-loving properties, or to a quick restitution from the lymph which is poured into the blood-stream. It has been observed both in dogs and men by Lyon19 that after a severe hemorrhage the number of red per cubic millimeter diminished for several days after the bleeding had been checked. How and where does the regeneration of red corpuscles take place after a severe hemorrhage? One would think that under these circumstances, if any, we should be able to get information which might be of service in determining the problem of blood-development; but, in spite of the numerous experiments on the subject, we are still far from a knowledge of full details. The observations of Neumann,20 Litten and Orth,21 Bizzozero,22 Lepine,23 and others appear to prove conclusively that the bone-marrow plays an important part in the formation of the new red disks, becoming lymphoid, losing its fat, and the nucleated red cells increase enormously. The same process has been observed in many cases in man. In a case of profuse metrorrhagia with profound anæmia Neumann24 found the marrow in all the bones of a rich raspberry red, full of the nucleated forms, which were also very abundant in the blood, and more in the vena azygos than in the aorta. The evidence in favor of the active participation of the spleen is not so conclusive. Neumann25 concludes that the spleen takes no share in the process, and holds that the nucleated red cells found in it are probably derived from the bone-marrow. Bizzozero, on the other hand, has found the spleen swollen and showing signs of lively blood-formation. He states that after removal of the spleen the restitution of the red corpuscles takes place much more slowly. Pouchet, on the contrary, says the regeneration goes on just as rapidly without the spleen. Of the action of the lymph-glands there is even less evidence. They have been found swollen, but in traumatic anæmia I do not know of any observations on their swelling and conversion into a red spleen-like tissue, such as have been found in some cases of idiopathic anæmia.
19 Of Norwich, Conn.: Virchow's Archiv, lxxxiv.
20 Archiv der Heilkunde, Bd. x.; Frerichs and Leyden's Archiv, Bd. iii.
21 Berliner klin. Wochenschrift, 1877, li.
22 Centralblatt f. d. Med. Wissenschaften, 1879, xvi.
23 Revue Mensuelle de Méd. et de Chirurg., 1877.
24 Loc. cit.