PLETHORA.
General and persistent polyæmia or plethora has scarcely a place in recent pathology. Formerly it was thought that either from over-production or lowered expenditure the total amount of blood accumulated and filled the blood-vessels to an abnormal extent. The amount of blood undergoes, within limits, constant daily alterations, and after a full meal the vessels are in a state of plethora compared with their condition at the end of a ten hours' fast. If a plethysmograph could be devised to record graphically the variations in the total quantity of blood, each ingestion of food or drink into the vessels would be followed by a rise, and each interval by a gradual decline. So long as the organs of secretion and excretion are active the quantitative and qualitative condition of the blood is maintained at a tolerably uniform standard in each individual. At different periods of life the relation of blood-weight to body-weight varies. In the new-born the blood amounts to one-eighteenth part by weight of the body, while in the adult the average is from one-twelfth to one-fourteenth; so that in the infant there is a condition of comparative plethora. There are no reliable observations on the proportion of blood- to body-weight at respective ages, but there appears to be a reduction in old age. In women it is stated that just before each menstrual period there is a state of polyæmia.15
15 Mary Putnam Jacobi, The Question of Rest for Women, New York.
Worm-Müller16 and Cohnheim17 have made some very interesting experiments on this question of plethora. By transfusion in dogs a state of artificial plethora is readily established, and the animals stand the injection of as much as 10 or 12 per cent. of the body-weight of blood, above which quantity a fatal result ensues. After an injection of 20 or 30 per cent. of the total amount of blood, the superfluous plasma and corpuscles are got rid of in a few days, while with a larger injection of 60 to 80 per cent. it takes two or three weeks before the normal state is again reached. The albuminous and nitrogenous materials are largely got rid of by the urine, which increases rapidly in quantity and also in the amount of urea. The excess of corpuscles gradually disappears, and the hæmoglobin becomes deposited, as Quincke has shown, in the form of small granules in the cells of the liver, spleen, and bone-marrow.
16 Transfusion and Plethora, Christiania, 1875.
17 Allgemeine Pathologie, 2te Auflage.
In a similar way, it is reasonable to think that the body is quite capable of disposing of surplus albuminous materials in over-fed, lazy individuals with active digestion, whose red faces, full vessels, and bounding pulses give the impression of a distended circulatory system, and whom we term plethoric. Their appearance is the result rather of blood-distribution than of actual increase in the total volume, and there is no evidence that under any circumstances a rich and abundant diet without much exercise can permanently increase the amount of blood. It was formerly held that the healing of an old sore or the cessation of an accustomed discharge or loss of blood, by diminishing expenditure while the blood-making power was maintained, could induce plethora if no local disorder was excited "before the vessels in general reached a state of plethoric tension." Of such a condition, and of the plethora apocoptica that was thought to occur after the amputation of a limb, we do not hear much now, and the prevalent opinion of pathologists is expressed by Cohnheim, when he says "that, except as a transitory state, polyæmia does not occur under any circumstances." What, then, is the meaning of the full-blooded, rubicund condition which we see in some men, not necessarily large feeders, but often with vigorous active constitutions and perfect types of health? The appearance of plethora is caused chiefly by the distension of the superficial vessels; the circulation of the skin is remarkably active, particularly in the face, and it is probable that we have here to deal with local peculiarities of the vessels or of their innervation, and not with any general augmentation of the total blood-mass. It may be, however, that in such persons there is a plethora of certain of the constituents of the blood—viz. the red corpuscles—and there may be a state of polycythæmia rubra, as it has been called, in which the percentage of red cells is increased. In several such cases I have found, as has been previously noted, the number of red corpuscles considerably over the average. A relative increase in the number of red corpuscles also occurs in those sudden and excessive losses of fluid, as in cholera, in which the blood may become thick and sticky from the great reduction in the plasma, particularly of the water and salts—anhydræmia—or in cases in which the income of fluid is greatly restricted. Henry (F. P.) has recorded a case18 of stenosis of the cardia, in which, with great emaciation, the corpuscles per c.m. were 5,525,000.
18 Archives of Medicine, New York, vol. vii.
The condition known as hydræmic plethora develops whenever there is a great reduction in the number of corpuscles, as after a hemorrhage, or when the blood has been impoverished by long-standing suppuration, albuminuria, or in the growth of large tumors. So also when the secretion of urine is diminished, as in some cases of Bright's disease, and at the same time charged with albumen, the blood may become very watery; but in these states there is not an absolute increase in the entire blood, but only a relative excess of the water. Occasionally, this great excess can be noticed in the blood-drop as it comes from the finger-tip; the corpuscles do not fill the entire drop, and consequently leave irregular areas unoccupied by the red disks.