32O PRACTICAL HISTOLOGY. fxXIX. 



2. V.S. Skin of Negro (H). Harden in alcohol, and stain the 

 sections slightly in eosin. Mount in balsam. Observe the granules 

 of melanin in the deepest layers of the epidermis. 



3. V.S. Skin of Finger (Double Stained). Stain a section first 

 in methyl-green iodide and clarify it with clove-oil coloured with 

 eosin. Wash out the clove-oil with xylol and mount in balsam. 

 The stratum corneum is green, and so are the nuclei of the other 

 epidermic and connective-tissue cells. 



4. Prickle-Cells and Touch-Corpuscles. Place in i per cent, 

 osmic acid or Flemming's fluid (24 hours) a very small piece of 

 fresh skin from the palmar surface of a finger. Wash it well in 

 water and complete the hardening in alcohol. Make V.S. and 

 mount in Farrant's solution. Or cut in paraffin, stain in safranin, 

 and mount in balsam. 



(a.) (H) Observe the various layers of the epidermis, but in the 

 Malpighian layer note the prickle-cells. The cells appear to bo 

 joined by their edges by fine striae, the striae leaving small spaces 

 between them (fig. 97). The striae are fine " intercellular bridges," 

 stretching from one cell to another, and it is only when the epi- 

 dermis is dissociated and the bridges broken that these cells appear 

 as cells beset with fine spines, and hence they were called " prickle- 

 cells." 



(b.) In a papilla search for a Wagner's touch-corpuscle (fig. 351). 

 It is an oval body, with its long axis in the long axis of the papilla, 

 but they are not present in all papillae (fig. 350). They consist of 

 a fibrous-looking material, with flattened nuclei arranged trans- 

 versely. To their lower end passes a medullated nerve-fibre, which 

 usually twists round the corpuscle before it enters it. The ultimate 

 distribution of the nerve is best seen in a gold chloride preparation 

 (Lesson XXXIV.). 



5. V.S. Foetal Skin for Sweat-Glands and Pacinian Corpuscles. 

 Harden the skin of the tips of the ringers of an infant in alcohol 

 and make V.S. Stain with hgematoxylin and eosin. 



(.) (L) Observe the general arrangement already described, but 

 the sweat-glands are much more closely placed than in adult skin, 

 and there is less intervening connective tissue. A child at birth 

 has its full complement of sweat-glands, and hence they must be 

 more crowded together than in the adult. 



(b.) In the subcutaneous tissue are lobules of fat and sections of 

 Pacinian corpuscles (Lesson XXXIV. 5). The latter appear to con- 

 sist of concentric laminae surrounding a central core. 



(c.) (H) Observe two or three layers of more or less cubical cells 

 lining the duct of the gland, while the true secretory portion is 

 lined by a single layer only of low, clear, columnar cells. 



Hair Follicles. To see their structure, harden the scalp in 



