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Only in this manner, by observing, namely, the earliest stages of the changes, is it possible to form certain and practically useful opinions with regard to pathological processes. Never ought one, basing one's opinion upon the difference of the processes in a clinical point of view, to allow oneself to be induced to regard their ultimate products as necessarily different. The most violent inflammatory processes which run their course in quite a short time, may have the same terminations as those which, in other cases, are brought about more slowly.

It is not my intention to go through the series of the different passive disturbances which may possibly arise in the later stages of irritative conditions, in detail. Else we should be able to discover analogous instances in the history of nearly all degenerative atrophies. In all cases we must discriminate between the conditions in which a part becomes directly the seat of such a retrograde metamorphosis, and those in which it previously underwent an active change.

The description which I have given you of the fatty processes directly applies to the class of calcifications. If it be wished to discriminate between ossification and calcification, it is not sufficient to keep the ultimate result in one's eye. A part does not become true bone, because it takes up lime into its intercellular substance and has stellate cells present in it; it may in spite of all this be nothing more than calcified connective tissue. When we speak of pathological ossification, we

with illustrations from the histories of patients and the results of post-mortem examinations (Archiv f. path. Anat. und Phys. vol. I, p. 134) as far back as 1847, or five years before Dr. Kirkes, to whom the honour of this discovery is still generally ascribed in England, published his papers on the subject. My observations concerning the detachment of thrombi in the veins were published a year earlier than this, viz., in 1846, and I then hinted at the occurrence of the same process in the arteries, although I did not give a full account of it until 1847 —From a MS. note by the Author.

CALCIFICATION AND OSSIFICATION OF ARTEBIES. 365

always presuppose that the mass which ossifies has been called into existence by an active process, an irritation, and not that a previously existing tissue assumes the form of bone, by absorbing calcareous salts. We have therefore calcifications and ossifications in the vessels. In ancient times everything was called ossification. Many of the more recent observers have denied that it ever does occur in vessels. Ossification does however really occur, but so does mere calcification or, as I will briefly term it, petrifaction. The latter is comparatively more frequent in the peripheral arteries, so that the condition which is generally regarded as a special criterion of the atheromatous process and in which the radial artery is felt to be hard and calcareous, and the femoral or popliteal is perceived to have hard and rigid walls, is no proof at all that the process is an atheromatous one. Very frequently this induration has its seat in the middle coat. In this case the calcification really invades the muscular elements, so that the fibrecells of the circular-fibre coat are transformed into calcareous spindle-shaped bodies. The calcareous matter may in these cases also invade the neighbouring parts, but the internal coat may possibly remain quite unaltered. This is a process therefore, which differs more from what is termed the atheromatous process than periostitis from ostitis. This species of calcification has no necessary connection whatever with an inflammation of the artery; it occurs most commonly in cases where there is a tendency to calcifications generally, and where calcareous salts are set free at other points in the economy and circulate with the juices. This much at least can with certainty be affirmed, that we are as yet acquainted with no stage in these changes, which is at all akin to inflammation.

On the contrary we see ossification declare itself in the internal coat of vessels in precisely the same manner as when an osteophyte forms on the surface of bone amidst all the phenomena of inflammation. The osteophytes of the inner table of the skull and of the cerebral membranes follow the same course of development as the ossifying plates of the internal coat of the aorta and even of the veins. They alwaysbeginwith a proliferation of the pre-existing connective tissue, whereby partial swellings are produced, in which the deposition of the calcareous salts does not take place until a late period. As soon as this real ossification exists, we cannot help regarding the process as one which has arisen out of an irritation of the parts stimulating them to new, formative actions; so far therefore it comes under our ideas of inflammation, or at least of those processes which are extremely nearly allied to inflammation. When a process of this sort is accessible to treatment, we always have other indications for practice, than in those cases, in which our object is, by the agency of stimulating substances, to prevent the occurrence of certain passive disturbances which hinder the part from discharging its natural functions.

What I have said will suffice, I think, to make these, in my opinion, extremely important distinctions clear to you. In the next lecture I will lay before you that one among the degenerative processes which is at the present moment the least clear, namely the lardaceous or amyloid degeneration.

LECTURE XVII.

APRIL 17, 1858.

AMYLOID DEGENERATION. INFLAMMATION.

Amyloid (lardaceous or waxy) degeneration.—Different nature of amyloid substances: concentric and laminated amyloid bodies (brain, prostate), and amyloid degeneration properly so-called.—Its course.—Commencement of the affection in the minute arteries.—Waxy liver.—Cartilage.—Dyscrasic (constitutional) character of the disease.—Intestines.—Kidneys: the three forms of Bright's disease (amyloid degeneration, parenchymatous, and interstitial nephritis).—Lymphatic glands. — Functional disturbances of the affected organs.

Inflammation.—The four cardinal symptoms and their predominance in the different schools : the thermic and vascular theory; the neuro-pathologists, exudations.—Inflammatory stimuli.—Lesion of function. — Exudation as a consequence of the activity of the tissues; mucus and fibrine.—Inflammation as a complex irritative process.—Parenchymatous and exudative (secretory) form.

I Will to-day, gentlemen, from among the changes which must in general be rather ranked with that class of degenerations which are attended with a diminution of functional power, introduce to your notice one, which has recently acquired especial interest, namely that which has been by some called the lardaceous (bacony—speckig), by others the way, whilst I have given it the name of the amyloid, change. The term lardaceous change has again come more into use chiefly through the instrumentality of the Vienna school. You know that the term itself is of tolerably ancient date in medicine as a denomination for a firm, compact, homogeneous appearance of parts. We find it has been employed for centuries, and, even in recent times tumours have been termed lardaceous. Still the term, lardaceous changes, as now used, has but very little to do with these tumours, and rather refers to things, upon which the old writers, who, I think, were better connoisseurs in bacon than our friends in Vienna, would hardly have bestowed such a name. The appearance of such organs, namely, as in accordance with Viennese ideas, are said to look like bacon, bears, according to northern notions, a much greater resemblance to wax, and I have therefore now for a long time, like the Edinburgh school, made use of the term waxy change instead. When we look at a liver or a lymphatic gland which constitutes a well-marked specimen of this condition, what strikes the naked eye most, is the translucent, but at the same time, dull appearance which the cut-surfaces exhibit; the natural colour of the parts is also more or less lost, so that a material, at first more of a grey tint, but afterwards perfectly colourless, seems to fill the parts. The translucent nature of the tissue allows, however, the red of the vessels and the natural hue of the neighbouring parts to glimmer through, so that the altered spots in different organs have rather a yellowish, reddish, or brownish tinge; but this is not a colour belonging to the substance deposited.

The first facts, by the help of which we were enabled to determine more accurately the nature of this substance, which had previously been taken, sometimes for a peculiar fatty matter, sometimes for albumen or fibrine, sometimes, finally, for a colloid substance, were furnished by the application of iodine to animal tissues. It will now soon be five years since I first discovered the peculiar reaction of the corpora amylacea found in the nervous centres with iodine, which I have already described to you, and since I had my attention directed to the extraordinary resemblance which

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