1092 
DR. H. WATNEY ON THE MINUTE ANATOMY OF THE THYMUS. 
take part in the formation of tubercle, as has been pointed out by Schuppel (90) and 
others. Again, in the observations which were made by Ziegler (88) on the formation 
of pathological connective tissue (his method consisted in introducing small glass plates, 
carefully cemented at the edges, into the abdominal cavity or, by preference, into the 
subcutaneous connective tissue); he found at first a number of small cells, which in 
his view gave origin to epithelioid cells and to granular cells (Bildungszellen) ; these 
two new forms of cell in turn become, in some cases, giant cells. Without expressing 
any opinion as to the actual origin of the epithelioid and granular cells which he 
found, it is at least quite evident that they could not have arisen from the remains of 
epithelial cells, either in the peritoneal cavity or in the subcutaneous connective- 
tissue. There is therefore no reason to believe because there are epithelioid cells in 
the thymus that they must have arisen from remains of epithelial cells which formed 
the original gland. 
Again, there is a remarkable similarity in the formation of fibrous tissue, as de¬ 
scribed by Ziegler (88) and Tillmanns (89) —the latter author introduced portions 
of hardened tissues into the abdominal cavities of Rabbits—to that which we have 
described in the thymus at pages 1086 and 1087, and represented in Plate 88, figs. 36 
and 38; the granular cells, in many cases, are seen attached by long processes, to 
newly-forming fibrous-tissue, and are evidently taking part in its formation. And 
there is an equally great similarity in the way in which the giant cells are formed 
in these pathological new formations to that in which they are formed in the thymus, 
as described at page 1088, and represented in Plate 90, fig. 50. 
Ziegler (88) and Tillmanns (89) consider that the granular and epithelioid cells 
are formed from colourless blood corpuscles. We have already shown at page 1087 
that we consider that in the thymus they arise from connective-tissue-corpuscles; but 
the after-steps of the formation of giant cells and fibrous-tissue from the epithelioid and 
granular cells appear to take place, in the thymus, in a very similar manner to that 
which has been described by those authors in pathological new formations. 
We may further add, that the study of the involution of the thymus, with its 
gradual transition into fibrous-tissue, will be, no doubt, of considerable value to 
pathologists. 
Ciliated Epithelium in the Thymus of the Dog. 
Remak (57) noticed (see History, p. 6) that in the Cat ciliated cysts are attached to 
the upper border of the thymus. 
In the thymus of the lower forms of Vertebrates, cysts are not uncommon. The 
ciliated cells in the Dog occur only in connexion with cysts, which are found in the 
interior of the follicles. w These cysts are never met with during the earlier periods of 
growth; they are always formed either from concentric corpuscles, or from masses of 
epithelioid cells, which become cysts without passing through the stage of concentric 
* I have examined the thymus of Oats of various ages, but have never fonndin them any ciliated cysts. 
