The atheromatous process consists in the metamorphosis (disintegration) of the deposit into a pulpy mass, compared by the French to a purée of peas, consisting of a large number of crystals of cholesterin, fatty globules, and of molecules exhibiting various degrees of consistence, from coarseness to extreme fineness, and consisting of albumen and calcareous salts.

The metamorphosis begins with a finely punctuated opacity and decoloration of the deposit, and it is not limited to any definite duration, occurring sometimes at an early stage, and at other times at a more advanced period, although, as has been already observed, generally when the deposit has become opaque. It, moreover, commonly begins in the deeper, older strata of the deposit, and advances from thence towards the surface. It usually affects a space varying in circumference from the size of a lentil to that of a crown or a shilling piece. There is, at the same time, an increase of volume, and a swelling of the deposit; the uninjured lamellae rising above the surface towards the interior in proportion to the depth to which the process has affected the deposit, and then frequently exhibiting a perceptible fluctuation.

After this process has penetrated to the innermost layers, or when they have burst above the pulpy mass, and been torn asunder by the force of the blood pressing into the cavity, the mass itself appears uncovered on the inner surface of the artery, and in contact with the blood, in which case fibrinous vegetationsof different forms are deposited on the fringed margins, after the occurrence of the bursting or rent.

The pulpy mass, both immediately after it has been laid bare and also subsequently, is taken up in different quantities into the blood, although another and the more consistent part of it is infiltrated by the blood, and permeated by its fibrin, and is thus rendered firmer, and, at the same time, colored by haematin, in various degrees of intensity, being first of a dark red, then of a dirty brown or purplish, and lastly, of a yeast-like color. In addition to these discolorations, the mass acquires a very peculiar appearance, when its surface is covered with large crystals and accumulations of cholesterin, for it then looks as if it were interspersed with spangles, or silver-like and shining scales.

These spots are even at the present day regarded as ulcers - fungous ulcers of the arteries. But the atheromatous process presents no essential analogy with an ulcerous process, nor is the deposit itself an inflammatory product. We discover no trace of an ulcerous product in the atheromatous mass, and its admixture with the blood is not characterized by any marked subsequent symptoms, as we learn from the experience of hundreds of cases.

The atheromatous mass is very often gradually thickened, and converted into a moist, soft, plaster-like substance; and finally appears in the form of a coarsely granular stalactitic calcareous concretion.

This loss of substance is occasionally replaced by a fresh deposit, when the atheromatous mass has either been wholly, or for the most part, taken up into the blood, in which case these spot3 remain below the level of the inner surface of the vessel, and thus acquire a cicatrix-like and wrinkled appearance, in consequence of the amount of shrivelling of the callous cellular sheath. They also very often acquire a slate-gray or greenish-gray, or black color from the haematin by which the tissue is saturated, and which remains on the margins and on the base. They are regarded as cicatrices of the supposed ulcers of the arteries.