Firstly

Typhus is characterized anatomically and in reference to the alterations in the solids, by the deposition of a peculiar product, which undergoes a peculiar metamorphosis.

Secondly

Its habitat varies and depends upon the specific relation existing between the general disease and certain organs. Indigenous as well as exotic typhus show the mucous membranes and the lymphatic glands to be the chief seat; in Austria it is chiefly the mucous membrane of the small intestine, yet even here bronchial and pneumonic typhus occur as a primary affection, and ought probably to be considered as the basis of the exanthematic form; we also, though very rarely, meet with colo-typhus.

Thirdly

The product of typhus presents in its first, but still more, in its later stages of metamorphosis, the greatest analogy with cancerous growths, and more particularly with medullary cancer.1

Fourthly

The local typhous process is a species of inflammation; but not one of those to which we attribute a phlogistic crasis of the blood, but one which, on account of the peculiar diseased condition of the blood, we term typhous.

Fifthly

The local affection of the mucous membrane of the small intestine, is a constant accompaniment of the typhus seen among ourselves; but as, according to our previous observations, it may occasionally be subject to an arrest of development, we find solitary exceptions in which there is no intestinal affection; in that case it is necessary to watch the other mucous membranes closely, or, indeed, the process, without being localized, may run its entire course in the blood.

It is well known that typhus occurs chiefly during the period of puberty and during the prime of life; before and after this epoch, it is very un-frequent; we must however guard against considering every typhoid appearance in Peyer's patches, during the early years of life, as genuine typhus. The predisposition seems to disappear with the involution of the sexual powers; still it does occur now and then, after the sixtieth and seventieth years of life.

Typhus presents a peculiarly interesting negative relation in reference to its capability of forming combinations. Pregnancy offers an almost entire immunity from typhus, lactation less so, and cases in which it is complicated with tubercular affections, with cyanosis, cancer and the cancerous cachexies are exceptional, whereas it is frequently complicated with syphilis and gonorrhoea.