(1.) Parietal.— These are in truth of ex treme rarity in the veins. That they do occur, however and with somewhat greater frequency than is a'dinitted by speculative writers, is cer tain. An example of " ossification" of the co ronary veins is related in the Ephem. Nat. Cur. Dec. iv. An. x. Obs. 175; Cruveilhiert once found the popliteal veins studded with ossifications similar to those existing in the accompanying arteries ; not a few examples of " ossification" of the vena porta are on re cord§ ; Morgagni and Baillie found the vena cava inferior in a similar state, Scc. In many cases of the kind there appears to have been calcification of the parts immediately adjoining the vessels.
The sort of antagonism existing between the arteries and veins, in respect of' parietal con cretions, has been referred by Bichat to differ ence of structure of the lining membrane in the two classes of vessel ; by Bizot to the dis similar properties of the blood circulating in them ; by others who regard the deposition as evidence of decay, to the greater activity and consequent earlier exhaustion of the arte rial tubes. None of these notions are unopen to objection.
(2.) Central. — Central concretions in the veins (pheboliths, from 0A.E11,, a vein, and Nieos, a stone,) are generally of ovoid or rounded shape ; vary in size from a pin's head to a pea and upwartls, in rare instances attaining the bulk of a hazel-nut, and in weight average about a grain or a little more at most ; are of low specific gravity; occur singly or in num bers varying from two to ten and upwards ; are either perfectly free, or adherent to the internal surface of the vessel either directly or by means of a slender peduncle (these three conditions may be observed in the same vein) ; are smooth on the surface, and (whether partly sanguineous or wholly calcareous) invested with a delicate membrane of serous aspect.
These concretions are unquestionably by far more common in the veins of' the pelvic viscera (the spermatic, the ovarian, the vesical, the hmmorrhoidal,) than in others. They are not unusual in the splenic veins, and have been met with in the renal, mesenteric, prostatic (thirty were found in the latter by Ehrmann 11), and pubic veins ; they have been seen twice by Cloquet in the vena cava inferior. They occur sometimes in varices of the lower ex tremities *; Dupuytren found them in the anterior and posterior tibial veins ; but they have not, so far as we are aware, been seen in the veins of the arms.
Gmelin found them composed of The part of the vein containing a phlebolith is sometimes much dilated, and eventually the vessel may become obliterated above and below the obstruction. Lobstein conjectures that the new formation with its investing portion of vein may be altogether separated from its con nections ; and, in the case of the limmorrhoidal veins, passed by stool.
Hodgson supposed that these bodies were first formed external to the vessel, and subse quently made their way into its interior ; An dral that their original seat was the substance of the walls of the vein. The occasional existence of a peduncle does not, as has been presumed, really warrant these notions ; as it may no doubt be formed either of fibrin or of plastic matter (thrown out by the tunics from secondary in flammation) coated with epithelium. Besides, the absence of marks of rupture of the surface further confutes them. It was suspected by Cruveilhiert, taught by Lobstein§, and proved by Carswel111, that phleboliths originate in clots in the interior of the vessels. The following is the series of changes observed :—stagnation occurs ; a clot forms; loses its red colour; becomes concentrically stratiform ; acquires fibrous consistence, and gradually grows calca reous and indurated, stratum by stratum, from the centre outwards, until the whole mass ac quires almost stony hardness. Dr. John Heidi regards the process of induration as one " re sembling the formation of osseous tissue in other parts of the body ;" a view invalidated by the absence of true cartilaginous matrix, or of osseous texture at any period of the evolution of the bodies in question.
(e.) Lymphatic and lacteal.— Althoueli it is possible that the extreme rarity with which the lymphatic and lacteal vessels have been found to contain calcareous matter may in part de pend upon those vessels being seldom ex amined, yet it is certain that such condition is really singularly uncommon. Cheston Browne** refers to a case in which the entire thoracic duct from the receptaculum upwards was "ossified " and obliterated. J. D. Scherbtt has described a concretion found in the tho racic duct. The lymphatics of the small in testines have been found in this condition by Walther.* The lymphatic glands, especially the bron chial and mesenteric, are, however, not unfre quently the seat of calcareous precipitation in points, patches, or through their entire sub stance ; it chiefly occurs in connection with tuberculous disease.