DR. H. WATNEY ON THE MINUTE ANATOMY OF THE THYMUS. 
1107 
We therefore conclude that the coloured blood corpuscles take origin, in part, at least , 
from large colourless cells. 
I wish to thank Mr. Dent, of St. George’s Hospital, and Mr. Compton for their kind 
help. 
Explanation oe Plates. 
The drawings, except where the contrary is stated, were made from sections of tissue 
hardened in chromic acid, and then in alcohol, and stained in hsematoxylin. 
The outlines of many of the drawings were made by means of an Oberhauser’s 
camera lucida, with a large Hartnack’s stand ; in such cases the lens (Hartnack’s) 
used with the camera lucida, and the approximate magnification, are given. The ocular 
and objective used in completing the drawings are also given. 
In other cases where the camera lucida was not used, the ocular and lens used in 
making the drawing are given with the magnification. These figures, however, are not 
drawn to scale. 
PLATES 83-95. 
Figs. 1, 2, 3, 4. Camera lucida, with a simple lens, magnified about 12J times. 
The four drawings show the appearance of the follicles in various stages of 
growth and involution. In each case the tissue was hardened for the same 
length of time in bichromate of potash and then in alcohol. 
The cortical portion of the follicles is distinguished in the drawings, as in 
the original, by its darker colour. 
The follicles are united by cortical-tissue at (a), by medullary-tissue at (b). 
In some follicles there are two or more portions of medullary-tissue, as at (c). 
ct. Interfollicular connective-tissue ; in figs. 2, 3, and 4 this tissue con¬ 
tains fat. 
ct'. Processes of the interfollicular connective-tissue, penetrating the cortex. 
Fig. 1. Section of the greater part of a lobule of the thymus of Calf three 
months old. 
Fig. 2. Section showing about two-thirds of a lobule of tbe thymus of 
Heifer two years old. 
Fig. 3. Section of thymus of Ox six years old. 
Fig. 4. Section of thymus of Cow, probably twenty years old. The vessels 
in the connective-tissue are very large. 
Fig. 5. Camera lucida,. simple lens X 12|. 
From Pay-fish, 4^ inches across. The section is vertical, parallel to the 
greatest breadth of the fish, and made a little behind the spout cavity. 
ca. Central cartilage. 
