186 PRACTICAL HISTOLOGY- 



in this is ready for embedding and making sections. 

 The piece from the palm of the finger is to be cut in 

 two directions, viz. (1) across and (2) parallel with 

 the ridges formed by the papillae. It will be easier 

 to cut a thin section if the razor is made to travel 

 from the corium towards the epidermis, rather than 

 in the opposite direction. The pieces of skin which 

 contain hairs should be so embedded as to carry the 

 plane of the vertical section in the direction of in- 

 clination of the hairs, so as to gain a view of the 

 hair follicles along their whole extent, and to show 

 the erectores pili if possible. 



The sections are in each case to be placed in log- 

 wood solution, and when sufficiently stained to be 

 washed in water and transferred successively to 

 spirit, oil of cloves, and dammar in the usual way. 



The preparations may be much improved, so far 

 as the exhibition of the epidermis is concerned, by 

 being placed in a saturated solution of picric acid 

 for about half an hour before being stained with log- 

 wood. In this way the horny parts acquire a bright 

 yellow color, which contrasts strongly with the violet 

 staining of the Malpighian layer. Owing to the num- 

 ber of nuclei which become stained in it, this part 

 of the epidermis is much darker than the papillary 

 part of the corium which is in contact with it. In 

 the papillae of the skin of the finger the tactile cor- 

 puscles may be sought for. They are generally 

 situated quite near the apex of the papilla, and to 

 see them well it is important to cut the papillae 

 exactly vertically, so as to include their length. In 

 sections which have been somewhat obliquely, and 

 in sections cut parallel instead of vertical to the sur- 

 face, the transversely or obliquely cut papillae appear 

 as round or oval islands in the midst of the deeper 

 cells of the epidermis. The dentated appearance 

 presented by most of the cells of the Malpighian 

 layer can readily be seen with a high power immer- 

 sion objective, 



Of the sections made from the skin of the finger 



