HISTOLOGICAL NOTES. TE 
animal. In both instances its structure is the same. In the 
adult its length is about 11 mm., its breadth about 7 mm., and 
its thickness between 2 and 8 mm. The size of the gland does 
not vary much in the young and adult animal, and, owing to its 
position and lobulated nature, cannot be easily distinguished on 
the naked-eye inspection from the salivary glands. Its structure 
is identical with that of the thymus of other animals, and like this 
consists of the connective tissue forming the capsule and the pro- 
longations of this into the interior as septa between the lymph- 
follicles. These latter are oblong, conical, cylindrical, or irre- 
gular in shape; they are of very various sizes, and their surface 
is either smooth: single follicles, or they are lobed, owing to 
more or less deep furrows, variable in number (two, three, and 
more up to ten), passing into the interior of the follicle: com- 
pound follicles. Where these furrows extend deep into the 
interior, the appearance is produced of a follicle being possessed 
of a number of secondary follicles, of very various sizes and 
shapes, and all projecting from the main body of the follicle. This 
appearance can be also interpreted by saying that a number of 
follicles have become more or less fused together. 
As regards the size of the follicles, it is difficult to make exact 
measurements, owing their very irregular shape. The following 
measurements are taken from a vertical section through the 
gland : 
One of the very large compound follices: length, 3°15 mm. ; 
breadth, 1:0]. 
Another large follicle: length, 2°92; breadth 1:23 mm. 
A very small follicle, the length, 1:01—1:23; breadth, 
0°68 mm. 
In a horizontal section, the length of a large follicle 2°7, the 
breadth 1°23 mm.; of a small one, the length 0°92, breadth 
0°53 mm. 
As regards the structure, the follicles completely coincide 
with those of the thymus. As in these, the outer part of the 
follicle z.e. the cortex of Watney, both in the single follicles as well 
as in the secondary projections of the compound follicles, stains 
deeper than the central part, z.¢. the medulla of Watney, which 
is non-transparent, and includes fewer small lymph-corpuscles 
than the former ; the medulla contains, like that of the follicles 
of the thymus in other animals, larger cells, with one, two, or 
more large clear nuclei, such as have been known previously, 
and have been more minutely investigated by Afanassiew 
(‘Archiv f. Mikr. Anatom.’ Band xiv), and Watney (‘ Proceed- 
ings of the Royal Society,” No. 187, 1878). Also the concentric 
bodies of Hassall are found in the follicles of the thymus in the 
guinea-pig. ‘Their structure is the same as of those described 
