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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 haematine. They therefore reach the bottom with comparatively great rapidity, whilst the colourless ones are still engaged in falling. If two bodies of different specific gravities be allowed to fall from a sufficient height in the open air, the lighter one will, you know, in a similar manner, reach the ground after the other, owing to the resistance of the air.

In the coagulation which takes

[graphic]

Fig. 60. Diagram of a bleeding-glass, with coagulated hyperinotic blood. a. The level of the liquor sanguinis, c. The cup-shaped buffy coat. /. 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 vensesection, 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 (Hsemitis)and established the doctrine of Pyaemia upon it, termed this form of bufly 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 Zimmermaun, 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.

LECTURE VIII.

MARCH 10, 1858.

BLOOD AND LYMPH.

Change and replacement of the constituents of the blood..-- Fibriue.—Lymph and its coagulation.—Lymphatic exudation.—Fibrinogenous substance. —Formation of the buffy coat.—Lymphatic blood, hyperinosis, phlogistic crasis.—Local formation of fibrine.—Transudation of fibrine.—Formation of fibrine in the blood.

Colourless blood-corpuscles (lymph-corpuscles).—Their increase in hyperinosis and hypinosis (Erysipelas, pseudo-erysipelas, typhoid fever).—Leucocytosis and leukaemia.—Splenic and lymphatic leukaemia.

The spleen and lymphatic glands as blood-making organs.—Structure of lymphatic glands.

The last time, gentlemen, I introduced to your notice the individual morphological elements of the blood, and endeavoured to portray their special peculiarities. Allow me to begin to-day with a few words concerning their origin.

From the facts which have been ascertained with regard to the first development of the elements of the blood, important conclusions may be drawn respecting the nature of the changes which take place in the mass of the blood in diseased conditions. Formerly the blood was regarded more as a juice shut up by itself, which was indeed to a certain extent connected with the parts external to it, but yet was in itself endowed with real durability, and it was assumed that it could retain peculiar properties for

ORIGIN OF BLOOD-CORPUSCLES. 167

lengthened periods, nay, that these might cling to it for many years. Of course it was impossible at the same time to entertain the opinion, that the constituents of the blood were of a perishable nature, and that new elements were added to it, to replace the old ones. For the durability of a part as such presupposes either that all its individual particles are durable, or that these individual particles are continually producing fresh ones within the part which bear impressed upon them all the peculiarities of the old ones. In the case of the blood, therefore, one would have to assume that its constituents really did subsist for years, and could for years present the same changes, or one would have to imagine that the blood transmitted something from one particle to another, and that from a parent blood-cell to its progeny something hereditary was handed down. Of these possibilities the former has, I believe, at the present time been pretty generally discarded. No one, I think, now imagines that the individual constituents of the blood last on for years. On the other hand, the possibility that the corpuscles of the blood are renewed by propagation, and that certain peculiarities which are introduced into the blood at a certain time, are transmitted from corpuscle to corpuscle, cannot straightway be rejected. But the only phenomena pointing to such a propagation of the blood, concerning which we possess any positive information belong to an early period of embryonic life. There it appears from observations which were only the other day again confirmed by Remak, the existing bloodcorpuscles undergo direct division, the process being that, in a corpuscle which during the early stages of its development had displayed itself as a nucleated cell, first of all a partition of the nucleus takes place (Fig. 51, e) ; and that then the whole cell becomes constricted in the middle, and gradually is really seen to pass into a state of complete division. At this early period it is therefore certainly allowable to regard a blood-corpuscle as endowed with qualities which are propagated from the first series of cells to the second, and from this to the third, and so on.

In the blood of a fully developed human being, nay even in that of a foetus in the later months of pregnancy, these phenomena of partition are no longer known, and not a single one of the facts which can be adduced from the history of development speaks in favour of an increase of the cellular elements taking place in fully developed blood by means of direct division, or any other formative process taking its rise in the blood itself. As long as the possibility was regarded as demonstrated, that cells might arise out of simple cytoblastema by means of the direct precipitation of different substances, so long was it possible to conceive new precipitates as forming in the liquor sanguinis from which cells were produced. But this view also has been abandoned. All the morphological elements of the blood, whatever may be their nature, are at present considered to be derived from sources external to the blood. On all hands recourse is had to organs which do not communicate with the blood directly, but rather by the means of intermediate channels. The principal organs which here come into play are the lymphatic glands. Lymph is the fluid which, whilst it conveys certain substances to the blood which come from the tissues, at the same time brings along with it the corpuscular elements out of which the blood-cells continually recruit their numbers.

With regard to two of the constituents of the blood, there can, I think, be scarcely any doubt but that this is the view which is perfectly warranted, I mean with regard to the fibrine and the colourless corpuscles. As for the fibrine, the properties of which I brought to your notice last time, it is a very essential and important fact that the fibrine which circulates in lymph differs in certain respects from that contained in the blood, which we see on exa

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