TERMINATION OF NERVES OF MAMMALIAN CORNEA. 461 
First, as to the relation of this stroma plexus to the sub- 
epithelial nerve expansion. 
Cohnheim (1. c.) traced from the most anterior branches 
of this plexus isolated twigs, which immediately underneath 
the epithelium split up into bundles of elementary nerve- 
librils. Hoyer Archiv f. Anat. and Physiolog.,’ 1866, Heft 
2) already saw these twigs ; and Kolliker Ueber d. Nerven 
Endigung in der Hornhaut Physic. Med. Gesellsch., in Wiirz- 
burg,’ 30th Juni, 1866), says of them that they pass in 
an oblique direction through the membrana Descemeti, in 
order to arrive at the posterior surface of the epithelium, 
and he therefore called them rami perforantes. Hoyer 
Archiv f. mikrosk. Anat.,^ ix, ii Heft, p. 236) was the 
first who described in the most anterior layers of the 
substantia propria, but underneath the anterior basement 
membrane, a special nerve termination, the subbasilar 
plexus, which consists of fine and finest fibrils derived from 
the branches of the stroma plexus. Most of the finest 
fibrils after a long, straight or wavy course and after 
branching terminate with free ends in the tissue. All fibres 
of the subbasilar plexus remain underneath Bowman’s mem- 
brane, and this plexus is densest in the peripheral zone of 
the cornea. While confirming Hoyer’s observation as to 
the great abundance of the fine and finest fibrils in this sub- 
basilar plexus in the cornea of the guinea-pig and rabbit, 
I am able to add to his description on some important 
points. 
I will here state once for all what in the following pages 
1 shall speak of thick and thin fibrils ; as I have attempted 
in my former paper (1871 and 1872) so also here I distinguish 
the nerve branches of the stroma plexus, each of which is in 
fact only a bundle of fine fibrils, as nerve bundles of the first 
order ; these give off fibres, which are to be considered as a 
small bunch of two or three primitive fibrils, are the nerves 
of the second order or the thick fibres^ and the individual 
fibrils constituting them are the fine fibrils or the fibrils of 
the third order. The latter are characterised by the smaller » 
and larger varicosities more or less closely placed. 
The fibres of this plexus are of various thicknesses be- 
tween that of a smaller branch of the stroma plexus and the 
finest fibrils marked by regular varicosities ; the thicker 
fibrils have only a short course, since they soon branch into 
the finer ones. But these latter are of various types, a. 
Such as take at once a bold straight course, as if they at- 
tempted to run to the furthest possible regions ; in this way 
they bend off from their course once or twice at a right angle, 
VOL. XX. NEW SER. II II 
