4. Erysipelas—a diffused redness, confined to a particular locality, with considerable tumefaction, and a sensation of super ficial hardness, appearing much more commonly about the bead and face than elsewhere. In deep-seated cellular inflammation there may be the same diffuse redness and tumefaction, but the sensation, on touching it, is rather that of tension than hardness : in the one, the skin itself is thickened by infiltration; in the other, the redness is only sympathetic, and the tension comes from the infiltration of the deeper lying structures, just as hap pens in the redness over a joint affected by acute rheumatism The degree of similarity which they present has led to cellular inflammation being called phlegmonous erysipelas ; it has none of the characters of an idiopathic fever, which have led to our placing erysipelas among the eruptive fevers. It is referred, along with the remaining acute exanthemata, roseola, urticaria, erythema, and eczema, to the division of diseases pertaining to the skin and cellular tissue. This classification seems objectionable, inasmuch as all of these are dependent on constitutional states ; but in the present state of our knowledge we must be content with such an imperfect arrangement.
Any evidence of fever which these cases present only proves it to be of a secondary character, and they do not differ in having a constitutional origin from other skin diseases, which must be classed according to their prominent symptoms, not according to their essential elements.
The more prominent complications of these several disorders have their uses in diagnosis, and therefore deserve enumeration.
1. Of measles—obstinate bronchitis, which often runs on to the deposition of raillery tubercle throughout the lungs.
2. Of scarlatina—suppressed action of the kidney, albuminous urine, dropsy.
3. Of smallpox—pleurisy, or pIeuro-pneumonia.
4. Of erysipelas, especially in dissipated habits—head symptoms, very analogous to delirium tremens. It does not appear that these are necessarily inflammatory, but they may be produced bhmeningitia, which is probably erysipelatous in its nature. (See Chap. XII. Div. I., Mental Functions. I 4, Delirium.)