TUBERCLE is a word that has been employed by pathologists of different epochs in very different seises. The older writers employed the term merely to express an external form; and everything was called a tubercle which manifested itself in the form of a small knot. Without entering into any discussion of the views of Laenneo (who asserted that tubercle presented itself in the lungs under two different aspects—nanzaly, as tubercular infiltration ned tubercular granulation, and thus opposed the oldknot theory), of Lebert (who was tf•e first accurately to describe the so-called " tubercle-cor puscles"), of Reinhardt (who, with many others, holds that tubercle is nothing more than one of the forms presented by :uflannuatory products when undergoing transforms tion, and that all tubercular matter is really inspissated pus), or of Rokitausky, Van Kolk, Williams, Walsh, Paget, and other eminent pathologists, we shall briefly give thr theory of tubercle which Virchow adopts it: his Cellular Pathology, and which is perhaps more generally adopted than any ether. Virchow holds that tubercle is a granule or a knot, and that this knot constitutes a new formation, which from the time of its earliest development, is necessarily of a cellular nature, ard like all other new formations, hat its origin iu connective tissue. When this new formation has reached a certain degree of development, it constitutes a minute knot; aod if it is near the surface, it forms a little protuberance, its mass consisting of small nucleated cells. The great characteristic of this formation is its extreme richness in nuclei, of which. at a first glance, it seems entirely to consist. But upon isolating the constituents of the mass, either very small cells with a single nucleus are seen, or larger cells with twelve, twenty-four, or even more divided nuclei are observed, these nuclei being always small, and having a homo geneous and somewhat shining appearance. In its minute nuclei and very small cells, tubercle contrasts strongly with the large and comparatively gigantic corpuscles of some of the more highly organized forms of cancer. To use the expressive language of Vir
chow; " tubercle is always a pitiful production, from its very outset, miserable." For an account of the cheesy metamorphosis which subsequently characterizes the tubercle, and which is the regular but not the invariable termination of this formation (since tubercle may undergo a complete fatty metamorphosis, and become capable of absorp tion, or may undergo calcareous degeneration, in which form it remains comparatively iuert), we must refer to the above-named pathologist's Cellular Pathology, translated by Chance (Loud. 1860), to Rokitansky's Morbid Anatomy, vol. i., and to Paget's Sur gical Pathology.
Tubercle is usually described as occurring in two principal forms, the first being dis tinguished as the yellow, and the latter as the gray; the latter is also known from its ordinary size as the miltary tubercle. The latter is the tubercle to which the above de scription of Virchow applies, the yellow being the same in a state of fatty degeneration or cheesy metamorphosis. In consumption, we often find large masses of softening tubercular matter in the lungs and elsewhere. These large masses are formed by the aggregation of smaller masses, which have coalesced as the deposit continued to incaease. The intervening tissues at length suppurate, and thus soften and break down the cular matter, and lead to its expulsion; for a process of ulceration having been estab• fished into the surrounding tissues, the softened tubercle is bi ought rip by coughing, and a cavity or cornice is formed at the spot previously occupied by the morbid deposit. It is a remarkable fact, and one of the greatest importance in the diagnosis of consumption, that tubercles, when they affect the lungs, are almost invariably deposited in the upper lobes. When it is stated that consumption is only one manifestation of scrofula (q.v.), and tub-rcle is the essential element of scrofula. it will be seen that the importance of this subject cannot be overrated. The reader may consult Mr. Ancell's elaborate volume. On Tuberculosis; or a clever essay, with a similar title, by Dr. Dobell.