1088 
DR. H. WATNEY ON THE MINUTE ANATOMY OF THE THYMUS. 
cells met with in the cortex are usually attached to the connective-tissue network (see 
Plate 89, fig. 39, a and b). 
The giant cells. 
These appear to he capable of division into two kinds, which differ somewhat in their 
appearance, the period of life at which they are formed, and their probable origin. 
In the foetal thymus, giant cells are found in considerable numbers (see Plate 90, 
fig. 50). They are large, very granular, and multinuclear; they are met with near 
granular cells, and appear to arise from them ; for in some cases we find granular cells 
of very irregular size and shape (see Plate 89, figs. 40 E and F, and 39 C and D); in 
other cases, granular cells containing two or three nuclei (see Plate 89, fig. 48; and 
Plate 90, fig. 49, gr); finally, we meet with preparations like those in Plate 90, fig. 50, 
gr, where a granular cell with three nuclei seems to be coalescing with other granular 
cells to form a giant cell. 
In animals, during involution, when fibrous-tissue is present in the organ, giant 
cells are met with close to the newly-formed tissue. They are much branched; the 
branches lie in several planes (see Plate 90, fig. 56 ; and Plate 91, fig. 57). In other 
specimens we find giant cells containing granular masses in their interior (see Plate 90, 
figs. 51, 52, and 53). Others contain cavities or gaps looking something like the 
lumen of a vessel (see Plate 90, figs. 51 and 55). This form of giant cell seems to arise 
from the network of connective-tissue-corpuscles, and we can trace the transition from 
masses of protoplasm containing many nuclei, to these giant cells. In Plate 88, fig. 30, 
at the left side of the figure, there are masses of protoplasm containing large granular 
cells. In Plate 90, fig. 54, is seen a newly-formed band of connective-tissue, et , and at 
right angles to it, and above it, multinuclear masses of protoplasm containing oval gaps. 
These masses of protoplasm in Plate 90, fig. 54, appear to be intermediate forms between 
the branched network of connective-tissue-corpuscles and the giant cells, and to 
account for the manner in which the gaps are formed in the giant cells, and for the 
presence of granular cells in the giant cells. 
Concentric corpuscles . 
The appearance of the concentric corpuscles, when large and fully formed, is very 
peculiar (see Plate 91, figs. 59, a, and 63). They consist of a central part and of 
outer layers, which latter we will for convenience call the capsule. 
The central mass is composed : sometimes (1) of small cells : at other times (2) of 
granular masses, which have many small nuclei imbedded in them; these nuclei are 
concentrically arranged, as at Plate 85, fig. 7, b : or again (3) of a mass of fine granules, 
as at Plate 85, fig. 7, g : but in general (4) of a homogeneous and strongly refractive 
substance, which presents no definite structure, and consists of two, three, or more 
parts (see Plate 86, fig. 15 ; Plate 90, fig. 50; and Plate 91, fig. 63). These central 
masses are often of a yellow colour, and contain haemoglobin granules (see Plate 86, 
