HISTOLOGICAL DEMONSTRATIONS. 99 



159. Pacini's Corpuscles. These may be obtained 

 by making a V. S. of the pad of the cat's foot, hardened in 

 chromic acid. Stain with carmine or logwood, and mount 

 in dammar. They may, however, be found with far greater 

 readiness in the mesentery of the cat, where they are evi- 

 dent to the unaided eye as small, clear, oval, bead-like bodies. 

 Examine a corpuscle removed with scissors from the cat's 

 mesentery, and placed in a drop of glycerine. 



(L.) The general appearance : nerve fibre entering at 

 one extremity, concentric layers of tissue covering it. 



(H.) The axial cylinder of trie nerve fibre in the centre 

 of the corpuscle. The medullary sheath disappears as the 

 nerve enters. The axial cylinder is surrounded by a layer 

 of finely granular substance, outside which there are a num- 

 ber of membranes that form a series of concentric tunics. 

 The fresh specimen may be fairly well preserved in 

 glycerine, but they are more perfectly preserved when 

 hardened in chloride of gold or chromic acid. 



Each tunic of the capsule of the corpuscle consists of an outer 

 and an inner layer of epithelial scales, with white and elastic fibres 

 surrounded by an albuminous fluid interposed (Key and Retzius). The 

 fibres may be demonstrated by teasing the corpuscle with needles after 

 maceration for a few days in ^ per cent chromic acid (Schaefer, Quart. 

 Mic. Journ., xv. 139). 



1 60. Nerve Terminations in Striped Muscle.- 



These may be most readily found in the muscles of the 

 thigh or back of the lizard (Lacerta viridis or Lacerta agilis\ 

 and in the recti muscles of the eyeball of a rabbit or other 

 animal. 



Examine (H.) a preparation made as follows : With 

 scissors make a thin longitudinal section of a rectus oculi 

 of a rabbit just killed ; place it in very dilute acetic acid 

 (two drops of pyroligneous acid in half an ounce of water) ; 

 and, after a minute or two, gently dissociate the fibres with 

 needles. On carefully looking along the fibres, profile 

 and superficial views of the nerve " end organs " may be 

 obtained. The nerve fibre penetrates the sarcolemma, 

 loses its medullary substance, and appears to end in a plate 

 of nucleated granular protoplasm that forms an eminence 



