The acute affection of the vena cava, which is minutely described by Aretæus, ought probably to be ranked with the diseases which we are now treating of. He himself is in doubt whether to consider it as a species of causus. Like the latter, he says, it has a tendency to pass into syncope. (De Sign. Morb. Acut. iii, 8.) He recommends for it venesection and the refrigerant plan of treatment. (Cur. Morb. Acut. ii, 7.) We have stated in the xxixth section that Palladius refers one variety of ardent fever to erysipelas of the lungs. A similar account of these affections is given by Avicenna, (iv, i, 4, c. 13, 14, and 15); and by Rhases (ad Mansor. x, 15, _alibique_.) We can draw no information from modern works to illustrate the opinions of the ancients respecting the febrile affections treated of in this section. It does not seem to be suspected now that erysipelas ever attacks the lungs or bowels; and yet, as this disease when it occurs externally is known to be seated principally in the epidermis, and as the epithelium, or membrane which lines the internal cavities, is admitted to be a prolongation of it, (see Kaau Boerhaave, Perspiratio Dicta Hippocrati,) it would seem probable _a priori_, that the diseases of both portions of it should be alike. That fevers are often complicated with ardent affections of the lungs and bowels, and bilious symptoms, we all admit; and it was, no doubt, to such febrile affections that the ancients gave the name of fevers from erysipelas—erysipelas, as we shall see afterwards, being referred by them to the state of the bile. One cannot but admire the sagacity of Hippocrates in tracing the connexion and resemblance between the diseases of the epidermis and those of the epithelium. (See Littré’s Hippocrat. t. iv, 419.) SECT. XXXII.—DIAGNOSIS OF HECTIC FEVERS.