214- PRACTICAL HISTOLOGY [XXVII 



5. Piece of mesentery of cat containing Pacinian 

 bodies treated with osmic acid and mounted in water 

 (or dilute glycerine). Note the bundle of nerve fibres 

 separating to the several Pacinian bodies. Some of the 

 fibres may divide and supply more than one Pacinian 

 body. 



6. Pacinian body after removal of the mesentery 

 treated with silver nitrate. Note the outlines of the 

 epithelioid cells of the outer capsules. 



7. Longitudinal and transverse sections of bed of 

 nail (picric acid ; picrocarmine). Note the upper clear 

 portion of the nail (corresponding to the stratum lucidum 

 of the skin), the Malpighian layer, and the longitudinal 

 ridges of the dermis. 



8. Skin of mammal with blood vessels injected. 



NOTES. 



Skin. 



Hardening. Mercuric chloride, picric acid and formol, 

 chromic acid, may also be used for hardening skin. Calleja's 

 stain (p. 311) gives good results. Thin sections of tissue 

 hardened in mercuric chloride may be stained with Mallory's 

 fluid (p. 311). 



In imbedding, the tissue should be left but a short time in 

 xylol and in melted paraffin, as in these it is apt to become hard. 



For prickle cells, sections of the Malpighian layer parallel to 

 the surface may be cut from skin fixed in osmic acid, and 

 mounted in glycerine-jelly. 



The horny layer will swell up and the cells show as vesicles 

 with sharply outlined walls, if a piece be cut off with a razor, 

 placed in 35 p.c. potassium hydrate for 10 to 15 minutes, and 

 then slightly teased in a drop of water on a slide. 



