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tralblatt,’ September, 1871). From the description of these we 
shall be able to deduce how far we are right in assuming the 
existence of free nerve-endings in the organs just mentioned. 
To obtain an easier view, we shall divide our subject into two 
parts. The first of these—the following paper—will treat of 
the nerves of the cornea, while in the second there will be 
discussed the nerves of the nictitating membrane of the frog, 
of the canal in the tail of the rabbit, and of the mesentery. 
Part I.—Nerves of the Cornea. 
After the well known and able description of the cor- 
neal nerves by Cohnheim (24), who has much enriched the 
knowledge acquired by his predecessors, His (25), Arnold 
(26), and Hoyer (27), it seems superfluous, if not ungrateful, 
to make these the subject of a treatise ; for the description that 
has been given by Cohnheim of the nerves of the cornea of 
mammals, including every detail, was in fact, by the adop- 
tion of the chloride of gold method introduced by him, con- 
firmed in most points by G. Kolliker (28) very soon after its 
appearance asa preliminary contribution. Nothing is indeed 
more easy than to convince oneself of the truth of the in- 
dividual assertions of Cohnheim. In undertaking, therefore, 
to produce something upon the subject of the nerves of the 
cornea, I do so for two reasons: first, I believe, as my pre- 
parations obtained by a somewhat modified method teach me, 
that I shall be able to examine the finest nerves of the cornea 
in their ramifications more perfectly and richly, and thus to 
make some not altogether unreal additions to our knowledge 
of them; and secondly, I have also obtained more complete 
specimens than have yet been described of the nerves which 
run in the substance and posterior portions of the cornea, 
and am therefore in a position to be able to contribute, if 
not much, yet something, about these nerves as an amplifica- 
tion of our present knowledge. 
First of all I might make some remarks upon the method 
which I have adopted. ‘To every one who has occupied him- 
self much with colouring with gold, and especially with the 
investigation of the nerves of the cornea by means of the chlo- 
ride, this has been a source of trouble, viz., that one obtains 
at times the greatest variety of preparations under otherwise 
similar modes of treatment, one has to wait frequently for an 
exceedingly tiresome length of time until the necessary colour- 
ing has been effected, one is so much dependent upon the influ- 
encing light, and is at times entirely destitute of success ; 
occasionally, also, the results are perfectly disproportionate 
to the time and pains bestowed upon the preparation. After 
