All the parts of the arterial system are subject to ossification. It appears as frequent in the branches as in the trunks. We know how common it is to find the radial ossified, in feeling the pulse of an old person. The ramifications appear to be less frequently the seat of these incrustations, which never take place in the capillary system; a circumstance that would induce me to believe that the common membrane of the arteries does not extend to this system, but that it changes gradually into a different texture. It is not only in the arteries that the common membrane of the system with red blood is penetrated with saline substance; this often happens to it in the heart, especially in the aortic and mitral valves. It is more rare upon the internal surface of the left ventricle and auricle and the pulmonary veins. I have had however examples of these last. This general disposition to ossification in its whole course, proves that its nature is every where the same, and that notwithstanding the differences pointed out, I have had reason to consider it in an uniform manner, from the pulmonary capillary system to the general; for as I have already observed, an identity of diseases supposes an identity of nature. It is the frequency of ossifications of this membrane in the heart of old people, which renders extremely frequent the intermission of the pulse at that age. The ossification of the origin of the aorta has an influence also upon the circulation, as I have ascertained; but that of the trunks, branches, &c. does not produce the least derangement.