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 TUBERCULOSIS — SCROFULOSIS.

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net-work of delicate fibres. There is much difference of opinion among- observers as to the presence, arrangement, and relative proportions of these elements ; and it must be borne in mind that they probably vary according to the seat of the tubercle, its age or stage of development, and the intensity of the tuberculous pro- cess. The lymphoid cells are generally considered to be most abundant, but Schiippel describes tubercle as being made up chiefly of epithelioid elements surrounding the giant-cell. This giant-cell has attracted much attention of late years. It occupies

Fig. ii.

Giant-ccIls. a. Rounded (Virchow); 6. With processes ; from a muscular tumour

[Diilroth].

the centre of each tubercle, and great importance was attached to it by Schiippel and others, but it has now been conclusively shewn that this element is not essential to the constitution of tubercle, and that it is found in many healthy and morbid structures, as well as in tubercle, so that it is by no means characteristic of this morbid product. Tubercle has been distinguished by some writers as celhdar and fibrous, according to the proportion of cells and fibrous reticulum entering into its formation, Friedlander, however, in- sists that in recent tubercle no fibres are visible, and that the appearance is due to the hardening processes employed in its preparation for microscopic examination. Tubercle does not con- tain any vessels or lymphatics of its own, but it may involve those belonging- to the original tissue in which it is formed; and it may also enclose pigmentary matters. As tubercle undergoes degen- erative changes, its microscopic appearances necessarily alter materially.

Changes and. terminations.— Some very important changes are liable to take place in connection with tubercle. i. Absorption. — It is probable that tubercle may be absorbed after it has undergone degenerative changes. 2. Caseous dcgaieration. — The want of vas- cularity, and consequent low vitality of tubercle, renders it very liable to this change. The deficient vascularity is probably mainly due to the pressure exercised by the cells upon the minute vessels,