144 
DR. A. WALLER ON THE MINUTE STRUCTURE OF THE PAPILLA 
lating to some extent the current of blood, and produce the turgescence of these pa- 
pillae which has been observed in the higher animals. The action of the cilia is very 
evident while under experiment. It conduces to clear away foreign bodies from the 
surface ; to equalize the distribution of the sapid substance over them, and conse- 
quently over the nervous extremities ; and to promote the removal of the epithelial 
scales which are constantly being shed. 
Nerves of the Papilloe conicoe . — The epithelial scales veil these in general so com- 
pletely that it is difficult to detect them. The application of the alkali which 
dissolves the seales, also disorganizes the nerves beneath. The plan which I find 
the most successful, is to macerate the part for an hour or two in saliva or water, 
when the increased transparency of the membrane renders the nerves more distinct. 
They are generally single, rarely two or three running together. Their course is 
irregular, wavy, with frequent simple loops, which enables them to present a much 
greater surface. In the tubule we frequently observe small granulations, but no 
white substance of Schwann is detected when perfectly fresh, although it frequently 
appears after the object has been kept for some time under examination. As a 
general rule in the conical papillae, the nerve-tube runs close to the aperture of the 
papilla around which it forms loops, after which it runs away in a wavy direction. 
Often at each angle of the aperture is a nerve-loop of this kind formed by separate 
tubes, besides others which are seen running in a meandering course, and crossing 
the former in various directions. The space enclosed by these nervous loops is much 
darker than elsewhere, as if it contained some dark granular matter. The tubes 
never appear to terminate abruptly in free extremities. They are derived from trunks 
which give off at nearly regular intervals two or three tubules closely joined together, 
which afterwards subdivide in a manner more and more irregular, till they reach the 
state of single nerve-tubules. 
It is evident that these are the nerves which convey the sensations of touch to the 
brain. The situation which they occupy at the base of the conical papillae under- 
neath the epithelian scales, can leave no doubt in this respect. It is true, that as at 
the base of the conical papillae, and immediately beneath the epithelian scales, we 
find striated muscular fibres running in various directions, and some ascending into 
the interior of the body of the fungiform papillae, it might be surmised whether these 
nerves are not destined to excite the contractile powers of these fibres. But their 
development, so utterly disproportioned to the office of stimulating a few muscular 
fibres, their mode of distribution in loops and convolutions, and their separation into 
single or double tubules, prevent our regarding them as muscular nerves. A curious 
point in reference to the nerves of touch, especially in the skin, are the fruitless 
attempts that have been made by numerous observers, to detect their ultimate 
terminations in the interior of the papillae. On account of the impossibility of 
seeing the nerve-tubules within the papillae, it has been imagined by some that they 
lose their external covering, and that they experience a gradual fusion with the 
