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of G. Zimmermann,1 who assumed that there were little vesicles present in the blood, which gradually grew by intussusception whilst circulating with it, and ultimately constituted the real blood-corpuscles. Now little corpuscles certainly do occur in the blood (Fig. M, h), only, when they are more accurately examined, a peculiarity reveals itself which is unknown in young embryonic forms, namely that they oppose an extraordinary degree of resistence to the most different agencies. In their ordinary state they are of a beautiful dark red, the colour being very intense and frequently nearly black; if they are treated with water or acids which dissolve the ordinary red corpuscles with ease, it is observed that the little bodies require a very much longer time before they disappear. Upon adding a large quantity of water to a drop of blood, they will be seen to remain for a considerable time after the other corpuscles have disappeared. This peculiarity accords best with what occurs in the changes which take place in the blood, when it is extravasated or remains for a long time stagnant within the vessels. Such changes undoubtedly lead to a destruction of the corpuscles, so that in the case of the circulating blood also the conclusion may with great probability be drawn, that the bodies in question are not young forms, engaged in development, but on the contrary old ones in process of decay. I agree therefore essentially with Karl Heinrich Schultz's view, who has described these bodies under the name of melanic (mclanose) blood-corpuscles, and regards them as the

1 Zimmermann has recently ('Archiv f. path. Anat. und Phys.,' vol. xviii, pp.221—242) given us a more explicit statement of his views, and from it we gather that he considers the blood-corpuscles to originate in small, colourless vesicles which are introduced from the chyle into the blood and may be seen in it when its fluidity has been preserved by means of salts. But probably these vesicles are only artificial products, similar to those described nearly ten years ago by Harting ('Nederl. Lancet,' 1851, 3rdser., 1st Jaarg., p. 224). —From a MS. Note by the Author.


precursors of the moulting of the blood (Blutmauserung)— preparing for the really excrementitious transformations.

There are certain conditions in which the number of these corpuscles becomes extremely large. In very healthy individuals very few of them are found, only in the blood of the vena porta? Schultz believes he has always observed a considerable number. It is certain, however, that there are diseased conditions in which their number becomes so large, that a greater or smaller quantity of them is met with in nearly every drop of blood. These conditions cannot however as yet be classed in definite categories, because but little attention has been excited with regard to them. They are found in slight forms of intermittent fever, in cyanosis after cardiac disease, in typhoid-fever patients, in the fever accompanying ichorous infection after operations, and in the course of epidemic disorders, still always in such diseases as are accompanied by a rapid exhaustion of the mass of blood and give rise to cachectic and anaemic states. This is one of the processes in which clinical observation also might lead to the conclusion that an abundant destruction was going on in the constituents of the blood within the vessels.

In addition to these changes we have precise knowledge concerning another class distinguished by quantitative changes in the number of the corpuscles. These conditions, of which Chlorosis is the principal representative, offer a certain resemblance to those which are accompanied by an increase in the number of the colourless blood-corpuscles, to leukaemia in a narrower sense of the word and the merely leucocytotic states. Chlorosis is distinguished from leukaemia by the circumstance that the entire number of the corpuscles is smaller. Whilst in leukaemia colourless corpuscles in some sort take the place of the red ones and a real diminution in the number of the cellular elements in the blood is not produced, in chlorosis the elements of both kinds become less numerous, without the occurrence of any definite disturbance in the numerical relation existing between the coloured and colourless corpuscles. This points to a generally diminished formation, and, if we may conclude (as I certainly think one can at the present moment scarcely help doing), that the red corpuscles also are brought to the blood from the spleen and lymphatic glands, all this would indicate that in chlorosis a diminished formation takes place in the blood-glands. Leukaemia is of course much more easily explained, inasmuch as in it we find representatives of the whole mass of cellular elements and can imagine that a part of them, instead of being transformed into red corpuscles, are pursuing their development as colourless ones. In the history of chlorosis, on the contrary, much obscurity still prevails, since we cannot positivelydemonstrate the existence of a primary affection of the blood-glands. Anatomical observations indicate that the foundations of the chlorotic ailment are very early laid; for the aorta and the larger arteries are usually, and the heart and sexual organs frequently, found imperfectly developed, facts which lead us to infer that the disposition is either congenital or formed in early youth.

A third series of conditions may here too be mentioned, which, however, do not affect the form of the blood-corpuscles, that, namely, in which the internal constitution of these elements has undergone changes, without the production of any definite morphological effect. Here we have essentially to deal with functional disturbances which are probably connected with more subtle changes in the composition of the blood, changes in the proper respiratory substance (respiratorische Substanz). For just as in muscles we find the substance of the primitive fasciculus, the compact mass of syntonine, to be the contractile substance, so in the contents of the red corpuscles do we

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recognize the presence of the really active, respiratory substance. This under certain circumstances undergoes changes which render it incapable of continuing its functions, a kind of paralysis, if you will. That something of the kind has occurred we see from the fact that the corpuscles are no longer capable of absorbing oxygen, as may be directly proved by experiment. That molecular changes in the composition of the blood are here really at work, we find satisfactory evidence in the action of poisonous substances which, even in extremely minute quantity, so change the haematine that it is thrown into a kind of paralysis. To these substances belong a part of the volatile compounds of hydrogen, for example, arseniuretted and cyanuretted hydrogen, and further, according to Hoppe's investigations, carbonic oxide, of all of which comparatively very small quantities are sufficient to diminish the respiratory power of the corpuscles. Analogous conditions have already long since been observed by manj in the course of typhoid fevers, in which the capability of taking up oxygen decreases in proportion as the disease assumes a severe and acute character. Microscopically, however, with the exception of a few melanic corpuscles, scarcely anything is to be seen; chemical experiment and the coarse perception of the naked eye in this instance alone discover the occurrence of peculiar changes. It may therefore be said that in this quarter really the most has yet to be done. We have rather presumptive evidence than facts.

If now we briefly sum up what I have laid before you concerning the blood, we see, either that certain substances find their way into it, which exercise an injurious influence upon its cellular elements and render them incapable of performing their functions; or that from a definite point, either from sources external to the body, or from some organ, matters are conveyed into it, which thence exercise an injurious influence upon other organs; or finally that its constituents are not replaced and regenerated in a regular manner. Nowhere in this whole series do we find any one condition, indicating that definite changes once set on foot in the blood itself can be permanently maintained, in other words that a permanent dyscrasia is possible, unless new agencies derived from a definite source are continually brought to bear upon the blood. This is the reason why I began by calling your attention to this point of view, which I conceive to be of extreme importance in practice also, namely, that in all forms of dyscrasiae the chief point is to search for their local origin.

Let us now proceed to the consideration of another subject which comes next in historical importance, namely the structure and arrangement of the nervous system.

The great mass of the nervous system consists of fibrous constituents. It is to them that nearly all the finer physiological discoveries, which the last fifteen years have brought with them, have reference, whilst the remaining portion of the nervous system, in quantity much smaller, namely, the grey, or ganglionic, substance, has hitherto opposed difficulties even to histological investigation which are still far from being overcome, so that the experimental examination of this substance has scarcely been able to be taken in hand. It is indeed often maintained that a great deal is now known about the nervous system, but our knowledge is for the most part confined to the white substance, the fibrous portion, whilst we are unfortunately obliged to confess that, both in an anatomical, but more especially in a physiological, point of view, we are still involved in the greatest uncertainties with regard to the grey substance, which, as far as its functions are concerned, manifestly holds a much higher position.

As soon as we consider the question of the influence exer

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