PROPERTIES AND FUNCTIONS OF NERVES. 95 



end plates /" when the nerve enters the muscular fibre the tubular mem- 

 brane blends with the sarcolemma, the medullary layer disappears, and the 

 axis cylinder spreads out into the form of a little plate, granular in charac- 

 ter, and containing oval nuclei. 



In the unstriped or involuntary muscles, the terminal nerve fibres form 

 a plexus on the muscular fibre cells, and become connected with the granu- 

 lar contents of the nuclei. 



In the glands nerve fibres have been traced to the glandular cells, where 

 they form a branching plexus from which fibres pass into their interior and 

 become connected with their substance, and thus influence secretion. 



Sensitive Nerves terminate in the skin and mucous membranes, in 

 three distinct modes, <?. g., as tactile corpuscles, Pacinian corpuscles, and as 

 end bulbs. 



The tactile corpuscles are found in the papillae of the true skin, especially 

 on the palmar surface of the hands and fingers, feet and toes ; they are 

 oblong bodies, measuring about ^ ^ of an inch in length, consisting of a 

 central bulb of homogeneous connective tissue surrounded by elastic fibres 

 and elongated nuclei. The nerve fibre approaches the base of the corpus- 

 cle, makes two or three spiral turns around it, and terminates in loops. 

 They are connected with the sense of touch. 



The Pacinian corpuscles are found chiefly in the subcutaneous cellular 

 tissue, on the nerves of the hands and feet, the intercostal nerves, the 

 cutaneous nerves, and in many other situations. They are oval in shape, 

 measure about the -fa of an inch in length on the average, and consist of 

 concentric layers of connective tissue ; the nerve fibre penetrates the cor- 

 puscle and terminates in a rounded knob in the central bulb. Their function 

 is unknown. 



The end bulbs of Krause are formed of a capsule of connective tissue in 

 which the nerve fibre terminates in a coiled mass or bulbous extremity ; 

 they exist in the conjunctiva, tongue, glans penis, clitoris, etc. 



Many sensitive nerves terminate in the papillae at the base of the hair 

 follicle ; but in the skin, mucous membranes, and organs of special sense 

 their mode of termination is not well understood. 



PROPERTIES AND FUNCTIONS OF NERVES. 



Classification. Nerves may be divided into two groups, viz. : 

 ( i ) Afferent or centripetal, as when they convey to the nerve centres the 

 impressions which are made upon ^their peripheral extremities or parts of 

 their course. They may be sensitive, when they transmit impressions which 



