820 



THE NERVE SYSTEM 



fibres the axone terminals form chains of flattened disks, the motor end plates. 

 Among gland cells the terminal fibrils form more or less intricate plexuses. 



Peripheral Nerve Beginnings of Centripetal Neurones. Nerve beginnings of the 

 centripetal (sensor) fibres are found in nearly all the tissues of the body. They 

 are peculiarly differentiated and of various forms in different localities, and their 

 function is apparently the conversion of mechanical, thermal, chemical, and other 

 stimuli into nerve impulses. The organs of vision, hearing, smell, and taste 

 possess variously modified nerve beginnings which are described under appro- 

 priate titles in the chapter on the Organs of Special Sense. The organs of the 

 centripetal neurones collecting bodily impressions (tactile sense, muscle sense) 

 and connected with the central axis are often very complicated structures. The 

 principal varieties are: 



Terminal fibrillse. 

 Tactile corpuscles (Meissner's). 

 "Ruffini's endings." 

 I. 4 Lamellated corpuscles (Pacini's). 

 Bulboid corpuscles (Krause's). 

 Genital (nerve) corpuscles. 

 Articular (nerve) corpuscles. 

 TT ( Neuromuscular spindles (Ruffini). 

 ' 1 Neurotendinous spindles (Golgi). 



Peripheral fibrillse are best demonstrable in the epithelium ,of the skin, mucous 

 membranes, and cornea. The axone is seen to break up into its constituent 

 fibrillse, which often present regular varicosities and anastomose with each other 

 in a plexiform manner. 



Tactile corpuscles (corpuscula tactus; touch corpuscles of Meissner and Wagner) 

 consist of elongated oval lobules of delicate epithelioid tissue invaded by one or 

 more axones which divide into their primitive fibrils, each terminal branch ending 

 free usually as a somewhat flattened, disk-like plate in among the wedge-shaped 

 cells of the corpuscle. Tactile corpuscles occur in large numbers in the cutaneous 

 papillae of the finger-tips, in the conjunctiva and, less abundantly, in the rest of 

 the skin; they appear to be concerned with the finer tactile sensations. 



"Nerve fibres. 



Peripheral ramifications 

 of axones. 



FIG. 591. Nerve ending of Ruffini. (After A. Ruffini.) 



Ruffini has decribed a special variety of sensor nerve beginning in the sub- 

 cutaneous tissue of the human finger (Fig. 591). They are principally situated 

 at the junction of the corium with the subcutaneous tissue; they are of oval 

 shape, and consist of a strong connective-tissue sheath within which the axone 

 divides into numerous varicose fibrils ending in small, free knobs. 



Lamellated corpuscles (corpuscula lamellosa; Pacinian corpuscles; Voter's 

 corpuscles; Herbst's corpuscles} are among the largest of the tactile end organs 

 and are found chiefly in the palmar surface of the hand, the sole of the foot, the 



