LECTURE VIII.

MARCH 10, 1858.

BLOOD AND LYMPH.

Change and replacement of the constituents of the blood.-Fibrine.-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 leukæmia.-Splenic and lymphatic leukæmia.

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

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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, c); 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 fœtus 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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mining different extravasations, or blood drawn from a vein. The fibrine of lymph has this special peculiarity, that under ordinary circumstances it coagulates within the lymphatic vessels neither during life nor after death, whilst blood in many instances coagulates even during life, and regularly does so after death, so that coagulative power is attributed to blood as being one of its regular properties. In the lymphatics of a dead animal or human corpse, no coagulated lymph is met with, yet the coagulation takes place directly the lymph is brought into contact with the air, or has changes imparted to it by some diseased organ.

The explanation of this peculiarity has been attempted in very different ways. For my own part, I must still adhere to the view that there is, properly speaking, no perfectly developed fibrine contained in lymph, but that it becomes perfect either by contact with the atmospheric air, or in abnormal conditions by the introduction into it of altered matters. Normal lymph contains a substance which is very readily converted into fibrine, and is, when it has once coagulated, scarcely to be distinguished from fibrine, but which, as long as it continues to circulate with the ordinary stream of lymph, cannot be regarded as really perfect fibrine. This is a substance, of which I had demonstrated the presence in various exudations, especially in pleuritic fluids, long before my attention had been drawn to its occurrence in lymph.

In many forms of pleurisy the exudation long remains fluid, and a number of years ago a peculiar case came under my notice, in which on puncturing the thorax a liquid was evacuated which was perfectly clear and fluid, but in a short time after its evacuation had its whole mass pervaded by a coagulum, as is often enough the case with fluids from the abdominal cavity. After I had removed this coagulum from the liquid by stirring it, in order to convince myself of its identity with ordinary fibrine, the

next day a fresh coagulum displayed itself, and this took place also on the following days. This coagulative power lasted fourteen days, although the operation had been performed in the midst of the heat of summer. This therefore was a phenomenon essentially differing from the ordinary coagulation of the blood, and somewhat difficult to explain upon the supposition that real fibrine existed completely developed in the fluid, but it seemed to indicate that it was only under the influence of the atmospheric air that the fibrine was produced from a substance which must indeed have been nearly related to fibrine, but yet could not be real fibrine. I therefore proposed to give it the distinctive name of fibrinogenous substance, and when I afterwards had come to the conclusion that it was the same substance which we find in lymph, I was enabled to extend my view so as to include the proposition, that in lymph also fibrine is not contained in a perfect form.

This same substance, which is distinguished from ordinary fibrine by its requiring to be a longer or shorter time in contact with atmospheric air before it can become coagulable, is also found under certain circumstances in the blood of the peripheral veins, so that even by an ordinary venæsection performed on the arm blood may be obtained, distinguished from ordinary blood by the slowness of its coagulation. Polli named this coagulative substance bradyfibrine. Such cases occur especially in inflammatory diseases of the respiratory organs, and most frequently give rise to the formation of a buffy coat (crusta pleuritica, crusta phlogistica). You all know that the ordinary crusta phlogistica forms in the blood of pneumonia or pleurisy the more readily the greater the wateriness of the liquor sanguinis, and the poorer the blood is in solid constituents, but it is an essential requisite that the fibrine should coagulate slowly. If the duration of the process be noted watch in hand, the conviction will soon be acquired that a