PHYSIOLOGICAL ANATOMY OF THE NERVOUS TISSUE. 



575 



Terminal Bulls. Under this name, a variety of corpuscles has lately been described 

 by Krause, as existing in the conjunctiva covering the eye and in the semilunar fold, in 

 the floor of the buccal cavity, the tongue, the glans penis, and the clitoris. They bear 

 some analogy to the tactile corpuscles, but they are much smaller and more simple in 

 their structure. They form simply a rounded or oblong enlargement at the ends of the 

 nerves, which is composed of homogeneous matter, with an exceedingly delicate invest- 

 ment of connective tissue. They measure from y^-^ to -^-Q of an inch in diameter. In the 

 parts provided with papillaa, they are situated at the summits of the secondary elevations. 



FIG. ISO. Cutaneous papilla and tactile corpuscle. 

 (Kolliker.) 



, cortical layer with plasmatic cells and fine elastic fibres ; &, 

 tactile corpuscle, with transverse nuclei; c, afferent ner- 

 vous branch, with its nucleated neurilemma ; c?, d, nerve- 

 fibres encircling the corpuscle ; e, the apparent termination 

 of one of these fibres. 



The arrangement of the nerve-fibres in these 

 corpuscles is very simple. One, two, or three 

 medullated fibres pass from the submucous 

 plexus to the corpuscles. The investing sheath 

 of the fibres is here continuous with the connec- 

 tive-tissue covering of the corpuscle, and the 

 nerve-fibres pass into the corpuscle, break up 

 into two or three divisions, and terminate in 

 convoluted or knotted coils. The nerve-fibres 

 are medullated for a certain distance, but their 

 terminations are generally pale. The above is 

 one form of these corpuscles. Sometimes, how- 

 ever, the terminal bulbs are oblong, and some- 

 times but a single nerve-fibre penetrates the 

 bulb and terminates in a simple pale filament. 

 The principal forms of the terminal bulbs are 

 shown in Fig. 181. 



General Mode of Termination of the Sen- 

 sory Nerves. The actual termination of the sen- 

 sitive nerves upon the general surface and in 

 mucous membranes is still a question of great 

 obscurity. Although we have arrived at a 



pretty definite knowledge of the sensitive corpuscles, it must be remembered that there 

 is an immense cutaneous and mucous surface in which no corpuscles have as yet been 

 demonstrated; and it is in these parts, endowed with what we may call general sensi- 



Fio.181. Corpuscles of Krause. (Ludden.) 



A, three corpuscles of Krause from the conjunctiva 



of man, treated with acetic acid ; magnified 300 

 diameters : 1, spherical corpuscle, with two 

 nerve-fibres which form a knot in its interior. 

 Portions of two pale nerve-fibres are also seen. 

 2, a rounded corpuscle presenting a nerve-fibre 

 and fatty granulations in the internal bulb; 3, 

 an elongated corpuscle with a distinct terminal 

 fibre. In these three corpuscles, the covering, 

 nucleated in 1 and 2, is distinguished. 



B, terminal bulbs from the conjunctiva of the calf, 



treated with acetic acid ; magnified 300 diame- 

 ters : 1, extremity of a nerve-fibre with its 

 bulb ; 2, double bifurcation of a nerve-fibre, with 

 two terminal bulbs; a, covering of the terminal 

 bulbs ; &, internal bulb ; c, 



