NERVOUS TISSUE 



159 



The stellate "Langerhans cells" shown in Figs. 146 and 147 are usually 

 regarded as wandering cells lodged in intercellular spaces, but Stohr states 

 that intergrading forms connect them with the epithelial cells; and they 

 may act as sensory cells. 



Muscle Spindles. As seen in ordinary preparations muscle spindles 

 are shown in Fig. 119 (p. 127). They are 

 slender groups of 3-20 muscle fibers, 1-4 mm. 

 long and 0.08-0.2 mm. wide, around which 

 nerve fibers terminate as shown in Fig. 148. 

 The spindles are surrounded by a thick connec- 

 tive tissue sheath or capsule, continuous with 

 the perimysium, and said to be divided into an 

 jt inner and an outer layer by a space filled with 

 fluid. The muscle fibers of the spindle are 

 poorly developed. They are distinctly striated 

 toward their tapering and very slender ends, 

 but in their middle portions, sarcoplasm and 

 nuclei are abundant and the striations ill de- 

 fined. Three or four nerves terminate in each 

 spindle. Their connective tissue sheaths blend 

 with the perimysial capsule, and they branch 



Tactile ce 



-it 



:-A 



Nerve fibrils. 



Connective tis- 

 sue sheath. 



FIG. 151. TERMINAL CYLINDER. 



(After Ruffini, from Ferguson's 



Histology.) 

 gH, Medullary sheath; il, terminal 



ramifications of the axis cylinder; 



L, connective tissue. 



FIG 152. TACTILE CORPUSCLE FROM A SECTION OF THE SKIN 



OF A HUMAN FINGER. X 560. 

 (Prepared by van der Velde, after the Bielschowsky method.) 



and lose their myelin as they pass through it to the muscle cells. 

 They may encircle the muscle fibers of the spindle, forming spirals or 

 rings (as in the upper part of Fig. 148), or they may form a panicle of 

 branches with enlarged club-shaped ends. Since they do not degenerate 

 after the motor roots have been cut, they are supposed to be sensory 

 fibers, but their function has not been established. Other sensory fibers 

 to muscle have free endings, as shown in Fig. 157. 



