XXVIl] SKIN. SENSORY NERVE ENDINGS 211 



4. Examine again the skin of the tip of a finger 

 (2). Observe the touch corpuscles. 



They are oval in form, and are found in the axes of 

 the papillae ; many papillae are without them, in which 

 case a capillary may generally be seen running up into 

 the papilla. 



They appear to consist of a mass of connective 

 tissue in which nuclei are disposed transversely. (For 

 the nerve fibre cp. Demonstration 2.) 



Pacinian bodies (cp. 5) may sometimes be seen in 

 the sub-cutaneous tissue. 



5. Examine the mesentery in a recently killed 

 cat ; in it will be seen a considerable number of oval 

 transparent bodies, the Pacinian bodies. (Some are 

 always present in the mesentery just above the inferior 

 mesenteric artery.) Select one which is not surrounded 

 by fat, cut it out and mount it in normal saline solution. 

 With a little care the mesentery covering it may be 

 removed with needles. Observe 



The medullated nerve fibre and the thickening 

 of its connective-tissue sheath as it approaches the 

 Pacinian body. 



The division of the connective-tissue sheath to form 

 the numerous concentric capsules, which become closer 

 together towards the centre of the body. At intervals 

 on the capsules elongated nuclei will be seen. 



The loss of medulla as the sheath splits up. 



The hyaline core inside the innermost capsule. 



The axis cylinder penetrating the core, and ending 

 in it in a slight enlargement. 



6. Treat a piece of skin of the face of a rat or kitten 

 (containing the whiskers) with gold chloride and formic acid 



142 



