practical fact cannot be interpreted in this way. It is not so much an increase of quantity, either in the blood as a whole or in that portion of it contained in an individual part, which is required in order that a like increase should forthwith take place in the nutrition of that part, or of the whole body, as that, in my opinion, particular conditions should obtain in the tissues (irritation) altering the nature of their attraction for the constituents of the blood, or that particular matters should be present in the blood (specific substances), upon which definite parts of the tissues are able to exercise a particular attraction.

If you apply this doctrine to the humoro-pathological conception of the processes, you will be able to deduce from it that I am far from contesting the correctness of the humoral explanations in general, and that I rather cherish the conviction that particular substances which find their way into the blood are able to induce particular changes in individual parts of the body by their being taken up into them in virtue of the specific attraction of individual parts for individual substances. We know, for example, that a number of substances are introduced into the body which possess special affinities for the nervous system, and that among this number again there are some which stand in a closer connection with certain very definite parts of the nervous system, as for instance with the brain, the spinal cord or sympathetic ganglia, and others again with particular parts of the brain, spinal cord, &c. On the other hand, we see that certain materials have some special relation to definite secreting organs; that they penetrate and pervade them by a kind of elective affinity; that they are excreted by them; and that, when there is a too abundant supply of such materials, a state of irritation is produced in these organs. But an essential condition in all these cases is, that the parts which are believed to have a particular elective affinity for particular matters, should really exist, for

SPECIFIC AFFINITIES.

KIDNEYS.

LIVER.

127

a kidney which loses its epithelium is thereby deprived of its secreting power. Another condition is that the parts should possess a relation of affinity, for neither a diseased, nor a dead, kidney has any longer the affinity for particular substances which the gland, when living and healthy, possessed. The power of attracting and transforming definite substances can be maintained at most for a short time in an organ, which no longer continues in a really living condition. We are therefore, in the end, always compelled to regard the individual elements as the active agents in these attractions. An hepatic cell can attract certain substances from the blood which flows through the nearest capillary vessel, but it must in the first place exist, and in the next be in the enjoyment of its special properties, in order to exercise this attraction. If the living element become altered, if a disease set in which causes changes in its molecular, physical, or chemical peculiarities, then its power of exercising this special attraction will at the same time. also be impaired.

Let us consider this example with still greater attention. The hepatic cells are almost in direct contact with the walls of the capillaries, from which they are only separated by a thin layer of delicate connective tissue. If now we were to imagine that the peculiar property possessed by the liver of secreting bile, merely consisted in a particular disposition of the vessels of the organ, we should indeed in no wise be justified in doing so. Similar networks of vessels, in a great measure of a venous nature, are found in several other places, for example, in the lungs. But the peculiarity of the secretion of bile manifestly depends upon the liver-cells, and only so long as the blood flows past in the immediate neighbourhood of the hepatic cells, does the particular attraction of matter continue which characterises the action of the liver.

When the blood contains free fat, we see that after a

time the hepatic cells take it up in minute particles, an that if the supply continues, the fat becomes more abun dant and is gradually separated in the form of largish drops within the hepatic cells (Fig. 27, B, b). That which we see in the case of fat in a more palpable form, we must conceive to occur in the case of many other substances in a state of more minute division. Thus for the due performance of secretion it will always be essential that the cells exist in a certain, special condition; if they become diseased, if a condition be developed in them connected with some important chemical change in their contents, for example, an atrophy, ultimately causing the destruction of the parts, then the power possessed by the organ of forming bile will at the same time continually become more limited. We cannot conceive a liver without livercells; they are, as far as we know, the really active elements, since even in cases in which the supply of blood has become limited owing to obstruction in the portal vein, the hepatic cells are able to produce bile, although perhaps not in the same quantity.

This fact derives peculiar value from its occurrence in the liver, because the matters which constitute the bile do not, as is well known, exist pre-formed in the blood, and we must therefore suppose the constituents of the bile to arise not by a process of simple secretion, but by one of actual formation in the liver. This question has, as you are aware, recently become invested with a still greater degree of interest in consequence of the observation of Bernard, that the property of producing sugar is also inherent in these elements, whereby the blood is supplied upon so gigantic a scale with a substance which has the most decided influence upon the internal metamorphic processes and upon the production of heat. If, therefore, we speak of the action of the liver we can, both in regard to the formation of sugar as well as that of bile, mean

SPECIFIC ACTION OF THE ELEMENTS OF TISSUES. 129

nothing but the action of its individual elements (cells), an action which consists in their attracting matters from the passing current of blood, in their effecting within their cavity a transmutation of these substances, and returning them in this transmuted form either to the blood, or yielding them up to the bile-ducts in the shape of bile.

Now I demand for cellular pathology nothing more than that this view, which must be admitted to be true in the case of the large secreting organs, be extended also to the smaller organs and smaller elements; and that, for example, an epidermis-cell, a lens-fibre or a cartilage-cell be, to a certain extent, admitted to possess the power of deriving from the vessels nearest to them (not always indeed directly, but often by transmission from a distance), in accordance with their several, special requirements, certain quantities of material; and again that, after they have taken this material up, they be held to be capable of subjecting it to further changes within themselves, and this in such a manner that they either derive therefrom new matter for their own development; or that the substances accumulate in their interior, without their reaping any immediate benefit from it ; or finally that, after this imbibition of material, even decay may arise in their structure and their dissolution ensue. At all events it seems necessary to me that great prominence should be assigned to this specific action of the elements of tissues, in opposition to the specific action of the vessels, and that in studying local processes we should principally devote ourselves to the investigation of of this nature.

processes

It will now, I think, be most suitable for us next to enter a little more in detail upon the consideration of the facts which form the basis of the humoro-pathological system,-upon the study of the so-called nobler juices. If the blood be considered in its normal influence upon nutrition, the most

important point is not its movement, nor the greater or less afflux of it, but its intimate composition. When the quantity of blood is great, but its composition does not correspond to the natural requirements of the parts, nutrition may suffer; when the quantity is small, nutrition may proceed in a comparatively very favourable manner, if every single particle of the blood contain its ingredients mixed in the most favourable proportions.

If the blood be considered as a whole in contradistinction to other parts, the most dangerous thing we can do is to assume what has at all times created the greatest confusion, namely, that we have in it to deal with a fluid in itself independent, but upon which the great mass of tissues more or less depend. The greater number of the humoro-pathological doctrines are based upon the supposition, that certain changes which have taken place in the blood are more or less persistent; and just in the very instance where these doctrines have practically exercised the greatest influence, in the theory, namely, of chronic dyscrasia, it is usually conceived that the change is continuous, and that by inheritance peculiar alterations in the blood may be transmitted from generation to generation, and be perpetuated.

This is, I think, the fundamental mistake of the humoralists, the real hinge upon which their errors turn. Not that I doubt at all that a change in the composition of the blood may pertinaciously continue, or that it may propagate itself from generation to generation, but I do not believe that it can be propagated in the blood itself and there persist, and that the blood is the real seat of the dyscrasia.

My cellulo-pathological views differ from the humoropathological ones essentially in this, that I do not regard the blood as a permanent tissue, in itself independent, regenerating and propagating itself out of itself, but as in a state of constant dependence upon other parts. We need only apply the same conclusions which are universally