MINUTE ANATOMY OF THE PAPILLAE OF THE FROG’S TONGUE. 
455 
Of the Capillaries. 
The capillaries of the papilla of the frog’s tongue are remarkable for their large size. 
In the common frog there is a complete vascular ring at the summit of the papilla, 
through which the bundle of nerve-fibres distributed to this part pass. In the Hyla the 
same is observed in some of the papillae, but the more common arrangement may be 
described as a half ring or a simple loop, bent upon one side at its upper part (Plate 
XXI. fig. 1). 
When the large capillaries of the papilla are distended with transparent Prussian- 
blue injection, their walls are seen to be of extreme tenuity and transparency. Con- 
nected with the transparent tissue are numerous oval masses of germinal matter (nuclei), 
which are separated from one another by very short intervals. Some of these masses 
project slightly from the inner surface of the vessel into its interior, but the majority 
seem to be upon its external surface. Of an oval form, many of these latter gradually 
taper into thin fibres which are continuous with the tissue of which the vascular wall is 
constituted. The delicate membrane constituting the vascular wall exhibits longitudinal 
striae, which are probably produced in its formation, and by its external surface is con- 
nected with the delicate connective tissue which forms, as it were, the basis-substance 
of the papilla, and intervenes between all the important tissues which are found in it. 
This is proved by the fact that the vessel is moved when the transparent connective 
tissue at some distance from it is drawn in a direction from the vessel. 
The most interesting point I have observed in connexion with the anatomy of these 
vessels, is the existence of very fine nerve-fibres. These form a lax network around the 
capillary. I have traced these fine fibres continuous with undoubted nerve-trunks in 
many instances, and have followed the latter into the trunks of dark-bordered fibres, 
from which the bundle in the papilla is derived. A similar arrangement of fine nerve- 
fibres has been demonstrated in connexion with other capillary vessels of the frog. 
These fine nerve-fibres are very distinct in several of my specimens. 
I have indeed observed, in my paper published in the Transactions for 1863, contrary 
to the statements of most anatomists, that capillary vessels generally are freely supplied 
with nerves, but the latter and their nuclei have been regarded as connective-tissue 
fibres and connective-tissue corpuscles ; I have shown in certain specimens that, of the 
two fibres resulting from the subdivision of a dark-bordered fibre, one was distributed to 
the fibres of voluntary muscle, while the other ramified over the vessels supplying the 
muscle (Plate XXII. fig. 15). These facts, it need scarcely be said, are of great import- 
ance with reference to the mechanism of nervous action. 
I have not succeeded in demonstrating lymphatic vessels in the papillae of the frog’s 
tongue. 
Besides the various nuclei described, there are several round, oval, and variously- 
shaped bodies, about the size of a frog’s blood-corpuscle, which are composed princi- 
pally of minute oil-globules and granules. These are not coloured by carmine. Many 
