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PROPERTIES OF COLOURLESS BLOOD-CORPUSCLES. 151

be found-a proof of the rapidity of the change to which these bodies are subjected.

Allow me, gentlemen, to add a few words with regard to the more palpable relations which the individual constituents of the blood present towards one another. It is, as you well know, generally assumed that of the morphological constituents only two are accessible to the grosser perception of the naked eye, namely, the red corpuscles in the clot, and the masses of fibrine, which under certain circumstances form a buffy coat, but that on the other hand the colourless cells are not to be perceived by the unaided sight. This is a notion which I consider myself bound to correct. The colourless corpuscles, whenever they are present in considerable numbers, become very distinctly manifest to the more practised eye during the separation of the constituents. of the blood, and especially when the coagulation is accompanied by movement; and they then exhibit a peculiarity, with which it is as well that one should be acquainted when one is required to pass judgment upon specimens derived from post-mortem examinations, and the ignorance of which has led to great

A

FIG. 58.

B

errors. The colourless corpuscles possess namely, as was brought to light in the discussion, which Herr Ascherson, now here present, had some time ago with E. H. Weber, the peculiar property of being sticky, so that they readily adhere to one another, and under certain circumstances also cling fast to other parts, when the red

Fig. 58. 4. Fibrine clot from the pulmonary artery, and corresponding to its terminal branches; at a, a beset with largish patches, composed of heaps of white cells, at b, b, b with specks of an analogous nature. Natural size.

B. A portion of one of these specks or heaps, composed of thickly crowded, colourless blood-corpuscles. Magnified 280 diameters.

corpuscles do not present this phenomenon. This tendency to adhere to other parts is particularly evident when several of the corpuscles are at the same time placed in a position which enables them to stick together. Thus, in blood in which there is an actual increase in the number of colourless cells, it is extremely common for agglutinations to take place among them, as soon as the pressure, under which the blood flows, is diminished; in every vessel, in which the stream becomes slower, and the pressure weaker, such an agglutination of the corpuscles may take place.

FIG. 59.

The adhesiveness (viscosity) of the colourless bloodcorpuscles produces besides this effect that, as has been shewn by Herr Ascherson, when the blood is flowing as usual through the capillary vessels, the colourless corpuscles generally float rather more slowly than the red, and that, whilst these move along more in the centre of the vessel in a continuous stream, a comparatively large vacuity is left at the circumference, within which the colourless corpuscles move, and that indeed often with such constancy, that Weber came to the conclusion that every capillary lay within a lymphatic vessel, in the inside of which the colourless blood- or lymph-corpuscles floated. But there cannot be the least doubt but that the

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canals in question are single ones, in which the

colourless corpuscles float along closer to the walls than the red ones; and it is in this peripheral space that, whilst the corpuscles move on, we see one here and there stick fast for a moment, then tear itself away and again move on slowly, so that the name of the sluggish layer (träge Schicht), applied to this part of the stream, has been universally adopted.

These two peculiarities, first, that, when the current becomes

Fig. 59. Capillary vessel from the web of a frog's foot. r. The central stream of red corpuscles. 1, 1, 1. The sluggish, peripheral layer of the stream with the colourless corpuscles. Magnified 280 diameters.

AGGLUTINATION OF COLOURLESS BLOOD-CORPUSCLES. 153

weaker, the corpuscles here and there cling to the walls of the vessel, and in some measure adhere to them, and secondly, that they gather together and become conglomerated into largish masses, combine to produce this effect, that, when there exists a large number of colourless corpuscles in the blood, and death occurs, as it does in ordinary cases, after a gradual weakening of the propelling force, the colourless corpuscles collect in vessels of every description, into small heaps, and generally lie upon the outside of the later formed blood-clot.

If, for example, we pull out of the pulmonary artery the generally very tough clot of blood which fills it, minute granules will perchance be found upon its surface (Fig. 58, 4), little beads of a white colour, which look like specks of pus, or are connected several of them together in the form of a string of pearls. This appearance most frequently presents itself at those points where the number of the bodies is normally the largest, namely in the interval between the orifice of the thoracic duct, and the capillaries of the lungs. The naked eye can with tolerable ease detect in these clots the greater or less quantity of colourless corpuscles. Under circumstances inducing the presence of a very large number of them, whole heaps of them may be seen, investing different parts of the coagulum like a sheath, and if one of these heaps be placed under the microscope, many thousands of colourless corpuscles are seen crowded together.

If the coagulation of the blood takes place, when it is more at rest, another appearance is presented with great distinctness, as may be seen in the vessels used to receive the blood after venæsection. When the fibrine does not coagulate very quickly, as is the case in inflammatory blood, the blood-corpuscles begin, in consequence of their greater specific gravity, to sink through the fluid. This subsidence proceeds, as is well known, to such a pitch, that, after

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the fibrine has been removed by stirring, the serum becomes perfectly clear, in consequence of the corpuscles' falling to the bottom. On defibrinating blood rich in colourless corpuscles, and allowing it to stand, a double sediment forms, a red and a white one. The red one constitutes the deeper, the white one the more superficial stratum, and the latter looks exactly as if a layer of pus were lying upon the blood. When the blood has not been deprived of its fibrine, yet coagulates slowly, the subsidence of the corpuscles does not take place so completely, but only the highest part of the liquor sanguinis becomes free from corpuscles; and when after this the fibrine coagulates, we obtain the well-known crusta phlogistica, the buffy coat, and on looking for the colourless corpuscles, we find them forming a separate layer at the lower border of the buffy coat. This peculiarity is simply explained by the different specific gravity of the two kinds of blood-corpuscles. The colourless ones are always light, poor in solid matter and very delicate in structure, whilst the red ones are as heavy as lead in comparison, owing to their richness in hæmatine.

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Fig. 60. Diagram of a bleeding-glass, with coagulated hyperinotic blood. a. The level of the liquor sanguinis. c. The cup-shaped buffy coat. 7. The layer of lymph (Cruor lymphaticus, Crusta granulosa), with the granular and mulberry-like accumulations of colourless corpuscles. r. The red clot.

PUS-, AND COLOURLESS BLOOD-CORPUSCLES.

155

place in blood derived from venæsection, this white clot does not usually form a continuous, but an interrupted, layer, composed of little heaps or nodules adhering to the under side of the buffy coat. Hence Piorry, who was the first to observe this appearance, but completely misinterpreted it, seeing that he referred it to an inflammation of the blood itself (Hæmitis) and established the doctrine of Pyæmia upon it, termed this form of buffy coat crusta granulosa. It really consists of nothing more than large accumulations of colourless corpuscles.

Under all circumstances this layer resembles pus in appearance, and since, as we have already seen, the colourless blood-cells individually are constituted like pus-corpuscles, you see that we are liable not only in the case of a healthy person to take colourless blood-cells for pus-corpuscles, but still more so in pathological conditions when the blood or other parts are full of these elements. You can imagine how apt the question is to present itself, which has already been seriously raised by Addison and Zimmermann, whether pus-corpuscles are not merely extravasated colourless bloodcells, or vice versa, whether the colourless blood-cells found within the vessels are not pus-corpuscles which have been admitted into them from the exterior. We are here called upon for the first time to make the practical application of the principles which I laid down with regard to the specific nature and heterology of elements (p. 64). A pus-corpuscle can be distinguished from a colourless blood-cell by nothing else than its mode of origin. If you do not know whence it has come, you cannot say what it is; you may conceive the greatest doubt as to whether you are to regard a body of the kind as a pus- or a colourless blood-corpuscle. In every case of the sort the points to be considered are, where the body belongs to, and where its home is. If this prove to be external to the blood, you may safely conclude that it is pus; but if this is not the case, you have to do with blood-cells.

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