1072 
DR. H. WATNEY ON THE MINUTE ANATOMY OF THE THYMUS. 
blood corpuscles escape from the vessels, and thus an increase of connective-tissue is 
set up; the new tissue presses on the concentric corpuscles, which gradually fade away, 
and thus few of them remain in the later stages. He injected the concentric corpuscles 
in five cases, and said that the smallest are in size and form similar to sympathetic nerve 
ganglia. Involution is produced by the decay of the vessels ; yet the presence of the 
concentric corpuscles is an expression of regressive metamorphosis. He found much 
pigment in the thymus of the Hedgehog; and in certain Mammals, round cells con¬ 
taining one or more coloured blood corpuscles. There is a fatty granular formation in 
the glandular elements; and fat arises in the pigmented cells, which are divided from 
the rest of the thymus by the bundles of connective-tissue running into the follicle ; 
the pigmented cells are very like those of the hibernating gland. 
Hahms (68), 1877, noticed a difference, in stained sections, between the outer and 
inner parts of the follicles, in animals of all ages; but thought the difference due to 
condensation of the glandular elements at the periphery of the follicle. She considered 
that the centres of the concentric corpuscles are filled by two or three spherical cells, 
but that they are formed by lymphoid cells ; and she fouud that there are more 
concentric corpuscles during involution than at other times. 
Watney (69), 1878, in a short note, showed that the follicles consist of two parts, 
which differ in the character of their network, and of the cells contained in their 
meshes, and in the arrangement of the blood vessels. He described granular cells, 
which help to form, partly by a process of vacuolation, the concentric corpuscles. These 
granular cells are attached to the blood vessels, and to the trabeculae. He found giant 
cells in the medulla, and stated that the concentric corpuscles are concerned in the 
formation of vessels and trabeculae ; and that in fresh preparations colourless cells are 
seen, which contain granules and spherules of haemoglobin. 
Klein (70), 1879, confirmed the fact of the existence of a cortical and medullary 
portion in the follicle. He said that in the medulla there are large endothelial cells, 
each of which fills up a mesh of reticulum; and there are transition forms between 
these and the granular cells, and between these last and giant cells. 
' Klein (71), 1881, found that the thymus does not much vary in the young and in 
the adult Guinea Pig. 
Watney (72), 1881, in a second short note, stated that there is an increase of con¬ 
nective tissue during involution, inside and outside the follicle ; that the cortical part 
of the follicle attains its greatest size at the period of the greatest activity of the gland ; 
and that the granular cells are actively concerned in the formation of connective tissue. 
A network of connective tissue corpuscles and a reticulum were described as both 
existing in the cortical portion. 
Watney (73), 1881, in a third short note, stated that the lymphatic vessels issuing 
from the thymus contain more colourless corpuscles than the lymphatic vessels of the 
neck ; and that in the thymus of the Hog ciliated epithelium can be found, if the 
animal be over a certain age. 
