1068 
DR. H. WATNEY ON THE MINUTE ANATOMY OE THE THYMUS. 
(a) in the same manner as the angiolithic sarcoma, Cornil and Ranvier (50), or (b) 
from the endothelium of the vessels, Afanassiew (51 and 33). (3) From the 
remains of the epithelium, from which the thymus is originally developed, TTth (52), 
1880, and Stieda (53). Kolliker (54), in 1863, said that they do not arise 
from gland cells. Their attachment to vessels was noticed by Berlin (31), His (46), 
and Paulizky (49). 
Bruch (43), 1850, noticed that the outer cells of the concentric corpuscles are 
epithelioid in character. He did not believe that the gland cells are changed into 
fat cells, as Simon (2) and many other authors had done ; but found fat cells in the 
connective tissue surrounding the follicles. 
Ecker (47), 1853, in a long paper, propounded the most definite and elaborate 
statements concerning the supposed cavity, comparing the thymus to an acinus gland. 
He thought that the gland consists of a central canal, closed at either end, into which, 
during its spiral course, many cavities open. He said that the vessels are outside the 
gland membrane. In describing involution, he found that points or streaks of fat 
pierce the gland tissue, while in the surrounding connective tissue the fat increases; 
that certain cells contain fat granules, and that there are intermediate forms between 
these cells and the concentric corpuscles, which he described as arising by fatty meta¬ 
morphosis of thymic corpuscles. He noticed the occurrence of pigment in the thymus 
of the Tortoise. He proved that the organ discovered in the Fish by Robin (38) is 
the thymus. At nearly the same time as Leydig (55) he described the position of the 
thymus in the Frog. He failed to find any difference between the fluid in the 
lymphatic vessels of the thymus and in those of other parts of the body. 
Gerlach (56), 1854, adhered to the view that cavities exist in the interior of the 
gland. He noticed that the vessel network is not so rich as had been imagined, and 
also that extravasations often occur in the central part of the follicle. 
Well (41), 1854, thought that the concentric corpuscles are endogenous formations, 
and gave good drawings of the large granular cells. 
Kolliker (48), 1854, described the thymus as being formed of lobes, connected by 
a canal which runs spirally in the interior of the gland. On the inner side of this 
canal he found openings, each of which leads into a lobule. He stated that the acini 
are solid (the acini in his drawings are, however, the cortical parts of the follicles). 
He noticed vessels penetrating the alveoli. He did not think it probable that there 
is a direct formation of blood corpuscles from thymic corpuscles, as Hewson (10) 
thought. 
Remak (57), 1855, described and figured ciliated cysts in intimate connexion with 
the upper part of the thymus of the young Cat. He compared them to the ciliated 
bladders of the mesogastrium of the Frog and the mesometrium of the Rabbit. He 
noticed a distinction between the cortical and medullary parts of tbe follicle. (See his 
plate 8, figs. 10a, 106.) 
Leydig (55), 1857, also described the position of the thymus in the Fish; he classed 
