CHRONIC ENDOCARDITIS.

Here we find a thickened condition of the endocardium, which is generally affected throughout the organ; the change is a chronic one, and consists in the formation of a homogeneous connective tissue between the muscle fibres and the endothelial lining of the organ; this change has no effect on the muscle fibres, but is simply continuous with the fibrous connective tissue existing between them; it is well supplied with blood vessels, which are in continuity with those in the muscle. In some places the endothelium is absent, and the growth takes a papillomatous form; at the base of these blood-clot is often seen. This clot becomes organized, and in this way the thickening is also increased. This must not be mistaken for acute endocarditis.

CHAPTER XXVI.

DISEASES OF THE ARTERIES.

IN studying diseased conditions of the arteries there are certain points in their normal histology to be remembered.

They have three coats:

1st. On the outside, the tunica adventitia, which is mostly composed of fibrous tissue.

2d. In the middle, the tunica media, which is composed of nonstriped muscle and elastic tissue in plates.

3d. The tunica intima, which is composed of the elastic fenestrated membrane of Henle, a very small amount of fibrous tissue, and on the inside the endothelial lining composed of flattened cells joined to each other by cement substance.

The nutrient vessels of the arteries run in the adventitia and send small branches into the media, which sometimes penetrate nearly through that coat.

The relative proportion in thickness between the middle and outer coats of arteries varies according to their size. In large arteries the muscular coat is much larger than the adventitia, and this is most marked in the aorta, where the adventitia is composed of only a small amount of fibrous tissue. The elastic tissue increases with the size of the artery, and in the aorta there is a large quantity.

HYALINE DEGENERATION OF ARTERIES.

As has already been mentioned in speaking of hyaline fibrous degeneration, a change of this kind occurs in the walls of arteries, especially in the ovary.

This change is also found in other parts and connected with new growths. Billroth gave it the name of cylindroma.

The morbid process consists in the conversion of the wall of the vessel, together with more or less of the surrounding tissue, into a hyaline-fibrous mass. This change, however, is not peculiar to the blood vessels (see Hyaline Fibrous Degeneration), but occurs in other tissues. It also does not affect all the vessels of a part, as some are

seen to be quite normal in close contiguity to others which are entirely changed by this form of degeneration. The whole of the wall of the vessel undergoes the change without blocking up the lumen-at any rate, in the early stages of the process.

Masses are also found running in tortuous arrangement, without any structures in them, and these may be changed vessels, but it is not probable. Examination with high powers shows no structure in the hyaline material, but it appears to be formed from the non-striped muscle fibres.

CALCIFICATION.

This degeneration occurs in the walls of arteries in two forms: As a deposit in the muscular fibres, without previous degeneration. As a calcareous deposit in newly formed fibrous tissue which has undergone fatty degeneration.

In the first form the deposit commences with the appearance of a few calcareous granules; these increase until the muscular fibres are infiltrated with lime salts, but still retain their normal shape; further deposit takes place and a calcareous plate is formed in the muscular wall of the vessel.

In the second form a fibrous change takes place first: new tissue is formed consisting of branched cells and corpuscles; these undergo fatty degeneration until a granular mass of débris is formed, which may undergo softening, and by opening into the lumen of the vessel cause the formation of a cavity in the wall, or the granular matter may become calcified.

This process is often described as fatty degeneration of arteries; but from a number of observations it seems that there is a fibrous change associated with the fatty.

SYPHILITIC CHANGES IN THE ARTERIES.

There are various changes found in the arteries in well-marked cases of syphilis; they may, however, be classified under three heads: Fibrous hyperplasia, with gummatous formations in the wall of the vessel.

Syphilitic endarteritis.

Fibrous degeneration of the smaller vessels.

The first form is best seen in the larger arteries, especially in the aorta. On opening the vessel a number of rounded elevations are

seen, some measuring half an inch in their longest diameter, or more, and raised about a quarter of an inch above the rest of the lining membrane. These raised patches occur in non-syphilitic cases, but are then different in their structure, being formed of fibrous tissue as described before. On making a section through the wall of the vessel transversely, passing through one of these elevations, the following changes are seen the whole elevation is formed by a new growth of fibrous tissue resembling myxomatous tissue, and this lies between the muscle coat and the endothelial lining. The new tissue consists of branched and round cells and fibrous tissue; at the inner part next the lumen the cells are few and the fibrous tissue fine and evidently newly formed; further outward, toward the muscle coat, a number of branched cells are seen, and numerous vessels in the process of formation. There is nothing in the growth itself to show its syphilitic character, but it is generally found in syphilitic patients. It also, as a rule, occurs in younger subjects than the other form, and is frequently associated with aneurism.

On examining the adventitia in the section the syphilitic nature of the change is seen at once. The adventitia is full of nodules formed of large, round cells, and these are undergoing degeneration in the centre; they resemble cascous miliary tubercle in an early stage except that the cells are much larger and many of them oval in shape.

SYPHILITIC ENDARTERITIS. (HEUBNER'S DISEASE.)

This consists of a growth between the membrane of Henle and the endothelial lining, which decreases the calibre of the vessel to a very large extent. It is best seen in vessels of the brain and is a certain sign of syphilis. It differs entirely from the ordinary form of chronic endarteritis.

The new growth is characterized by the presence of large, round or oval cells, of which it is largely composed, and there is little fibrous tissue, and that of a delicate form.

The third form is well shown in the brain and testes in cases of death from syphilis, also in the testes in syphilitic orchitis.

The change consists in the formation of fibrous tissue in the intima of the smaller vessels; this grows in loops from all sides until the lumen of the vessel is completely obliterated.

Large tracts are filled with vessels having undergone this change and the tissue surrounding them is also changed into a form of fibrouslooking material containing large cells, so that it is impossible to

distinguish between sections of brain and testes when taken from the diseased parts.

In syphilitic orchitis the change is also very marked, a wedgeshaped mass running across the organ containing nothing but a fibrous matrix with tubes blocked, as described above; in this case probably the seminiferous tubules undergo the same change as the blood vessels. The morbid process affects veins as well as arteries.

CHRONIC ENDARTERITIS-ENDARTERITIS OBLITERANS.

This is a morbid process affecting arteries throughout the body; it is a chronic inflammatory change caused by an altered condition of

Chronic endarteritis. Artery in a kidney affected with interstitial nephritis. X 130. The muscular coat is not hypertrophied.

the blood; it is associated with various diseases, but is commonly seen in conjunction with chronic disease of the kidney. (See Chronic Bright's Disease).