404 DR. E. KLEIN. 
regards the relation existing between the interstitial substance 
of the epithelium of the mucous membrane of the frog’s 
mouth with the tissue of the latter. 
42. In vertical sections through the injected tongue we 
see, under the microscope, a very rich plexus of lymphatics 
situated in the thin mucous membrane; these vessels are 
very irregular in size and outline, and some of them possess 
valves. Their course is chiefly parallel to the surface, and 
both in longitudinal as well as in transverse sections through 
the tongue a great many vessels are seen cut longitudinally. 
Sappey describes fine vessels which enter the papille and 
then form a network. I can fully confirm this, for I find 
that each papilla filiformis and fungiformis (which, as is well 
known, are again possessed of minute secondary papilla) of 
the human tongue contains its own network of lymphatics. 
From the network we see lymphatic vessels ascending the 
secondary papille and either terminating in a cecal extremity 
or in a loop. 
In animals (dog, rabbit) this is in so far different, as the 
filiform papille are mostly simple, not compound, but in the 
fungiform papille the same relations exist as in those of the 
human tongue. 
43. The papille circumvallate of the human tongue 
contain a very great number of lymphatics. They are all 
fine vessels connected into a network, which does not show 
any special richness at the base where the taste-goblets are 
found; on the contrary, the vessels are if anything less 
numerous at that part than at the rest of the “ papilla.” 
In the papilla foliata of the rabbit each of the ridges, 
which constitutes this organ, and as is well known, corres- 
ponds to the “ papilla” of a circumvallate papilla drawn out 
into a fold, contains at its basis rows of taste-goblets ; we 
find here in so far a variation of the above arrangement of 
the lymphatics, as from the superficial network there 
generally ascends in the centre of each of the folds a cleft- 
like or sinuous lymphatic which terminates in a cecal 
extremity near the top of the fold, but does not reach as 
high as the blood-vessels. In some folds small branchlets 
may be found to come off at the basis from the central 
vessel ; they then ascend towards the taste-goblets; it is not 
possible to ascertain whether they stand in any definite 
relation to the latter. 
44, At the root of the human tongue, where the mucous 
membrane contains masses of adenoid tissue, either diffuse 
or as more or less well-defined lymph-follicles, this arrange- 
ment of the lymphatics in so far suffers an alteration as their 
