gg NORMAL HISTOLOGY. 



also pass between the adjacent lamellae. After silver stainings the 

 corpuscles of Vater appear to be completely invested with a mosaic 

 of endothelial plates ; these markings are due to the cells which line 

 the inner surface of the outer lamellae. 



The core of the corpuscle is occupied by a light granular or faintly 

 striated cylindrical mass the'inner bulb composed, seemingly, of 

 an almost homogeneous tissue, closely resembling protoplasm, in 

 which nuclei and indistinct fibrils sometimes are seen. Within and 

 corresponding to the axis of the inner bulb lies the free axis- 

 cylinder, ending frequently in a slightly expanded terminal knob ; 

 the medullary substance surrounds the axis-cylinder as far as the 

 inner bulb, where it disappears. The small artery usually accompany- 

 ing the nerve-fibre within the stalk of the corpuscle gives off fine 

 branches to be distributed to the outer layers of the capsule. 



The corpuscles of Herbst, found in birds, closely resemble the 

 Valerian corpuscles of mammals, possessing, however, a less devel- 

 oped capsule and an inner bulb beset with a single or double row 

 of nuclei. 



From the foregoing sketch it will be seen that, taking the tactile 

 cells as a ground-form, the special nerve-endings are developed along 

 two lines : one type is represented by the spherical tactile cor- 

 puscle, composed of winding nerve-fibres bearing tactile disks 

 placed between tactile cells and enveloped within a capsule ; the 

 other by the cylindrical end-bulb, in which the central nerve- 

 fibre lies within a cylindrical inner bulb, enveloped by a capsule 

 developed to a greater or less degree. As the highest representative 

 of the first group stand the complex tactile bodies of Meissner ; of 

 the second group, the corpuscles of Vater. 



The following table indicates the relations of some of the principal 

 forms of special sensory nerve-endings : 



Simple Tactile Cells. 



( Ground- Form. ) 

 Epidermis of man and mammals. 



Compound Tactile Cells. 



Grandry s Corpuscles: Epidermis of birds. 

 Merkel 's Corpuscles: Epidermis of mammals. 



Tactile Corpuscles. 



(Spherical.} 



Spherical End-Bulbs : Conjunctiva and mucous membranes of 

 man. 



