harder, or, from degeneration, softer. The specific lesion of leprosy differs from that of tubercle inasmuch as the former is well supplied with blood-vessels, contains no true giant cells, and never undergoes caseation. If hardened, cut, stained, decolorized, and examined under the microscope, the leproma is found to consist principally of small round cells about the size of a leucocyte, epithelioid cells, and fusiform cells the two latter in numbers increasing with the age of the leproma. It can be seen that these cells have infiltrated and partially dissociated all but the most superficial layer of the derma. It may be further observed that the cells are arranged for the most part in groups, generally around and near blood-vessels; and that a very large proportion of them contain bacilli, some cells having only a few, whilst others are literally crammed with the organisms. Isolated bacilli are also found scattered through the preparation, apparently free in the lymph spaces. The bacilli are never seen inside the nuclei of the implicated cells.
In addition to the bacilli-bearing cells, and increasing in number with the age of the lesion, a number of brown granular bodies, larger and smaller, which have been named " globi," are to be found. These Hansen holds to be cells in which the bacilli have perished and become granular. It is to them that the brown colour of old lepromata is due.
There has been considerable discussion as to the exact position of the bacilli as regards the lepra cells —whether they lie inside the cells or whether they are free. On the one hand, Unna holds that they lie free in the lymph spaces, and that they are never in the cells, the appearance of cell inclusion being produced by the zooglœa arrangement so common with bacteria. On the other hand, Leloir maintains that some of the bacilli are free whilst others are inside the cells. A third set of observers, following Hansen, hold that the bacilli are almost invariably included within cells, the nuclei of which can readily be demonstrated surrounded by the parasites.
Other lesions.— The histology of the infiltrated macula is practically the same as that of the leproma,
