To this class belong all acute and chronic exanthematous processes which present the following general characters. They are preceded or accompanied by symptoms of inflammation: either at one spot, or at several, separate or clustered points, they furnish a product: sometimes that product takes the form of vesicles and bullae, and lies between the cuticle and cutis; sometimes it occupies the parenchyma of the cutis, being effused amongst the papillae, or in the deeper layer, and forming nodules that either subside again, or suppurate and produce small abscesses or pustules; and sometimes, lastly, it gives rise to induration of the skin, to nodules and nodular thickening of the subcutaneous cellular tissue, and their usual consequences, suppuration, ulceration, or hardening.

The present appears to be the most convenient opportunity for alluding to these processes; for anatomy has not yet furnished satisfactory evidence as to their real site, whether it be the different glandular organs of the skin and their ducts or not. I venture, however, to omit giving any minute description of them, not for this reason merely, but also because we possess only a few fragments of anatomical information respecting their products; and further because the changes in the internal organs, which have hitherto been observed after death, - changes, that is, essentially connected with the disease of the skin, and constant in their occurrence in many of these cases, though not, indeed, in all of them, - do not furnish facts in sufficient number and of a kind to allow of our constructing an account of their pathological anatomy, that would make any pretensions to truth and to practical utility.

The last remark applies particularly to those exanthematous diseases which are usually treated of amongst chronic diseases of the skin, for several of those which are now under consideration, as well as of the acute processes spoken of under the head of erythematous inflammations, are frequently fatal, and consequently become the subjects of pathological examination, especially true variola and scarlatina.

Although much has already been said, and some remains still to be said on the subject, it will be proper to mention here, in general, some of the principal results of examinations of the body in the cases of exanthema, that have been mentioned.

With an exanthema upon the skin that is discolored, collapsed, and sometimes scarcely perceptible, are connected erythemata and exudative and pustular inflammations upon the several mucous membranes adjoining the external integuments. They take place especially on that of the mouth, pharynx, trachea, and bronchi, as well also as that of the urethra and vagina; they are complementary to the cutaneous eruption, and may be more or less substantive in their character; but frequently they are extremely developed both in extent and in the degree of their intensity.

Next in order may be placed the more or less palpable developments of the follicles of the intestines, especially those of the ileum; after these, similar developments of the mesenteric glands: and then congestions and enlargements of the spleen.

These may be followed by congestions of the central organ of the nervous system, and of its membranous investments; and very commonly, too, by increased density of the cerebral substance, with the exception of cases to be mentioned afterwards.

And next may be mentioned exudative processes upon mucous and serous membranes, especially on the former: some of these are genuine croupy exudations on the divisions of the mucous system above mentioned, as croupy pneumonia, croup in the oesophagus, stomach, and intestines; others are gelatinous, purulent or serous exudations, and are found particularly on the mucous membrane of the bowel, and in the parenchyma of the lungs, - pulmonary oedema; others, again, are exudations upon serous membranes, especially upon the arachnoid, where they are accompanied with a turgid, moist, and loosened state of the cerebral substance, - oedema of the brain; some are met with on the pleurae, etc, and even upon the internal surface of the vessels (phlebitis).

The acute black softenings of the cardiac portion of the stomach, and of the oesophagus may be arranged next; and then - Gangrene on the general integuments and in the internal organs.

Changes of the mass of the blood take place in the dead body parallel with these processes in the solids. The fibrin has a marked tendency to coagulate; the blood is deprived of its fibrin; or the latter is fluid; or the blood contains no coagulable part, but is either no thicker than water, or thick, viscid, like tar, and of a purple-red color, inclining to bluish, violet, black, etc. With the changes last described, are connected marked collapse of the body, lividity of the integuments (especially of the exan-thematous part), and of the muscles, red transudations into the serous cavities and into the tissues, and particularly the escape of blood into the parenchyma of membranous expansions, in the form of ecchymoses, petechiae, suffusions, etc, especially on the skin.

As the exanthematous, especially the acute exanthematous processes are allied in their nature to the exudative, I must here refer to yet one septic exudative process which takes place upon skin deprived of its epidermis, and which is closely analogous to sloughing croup1 (Bretonneau's Dyphtheritis): it is that which is named hospital gangrene.