68 



This preparation affords a demonstration of the transition of the 

 epidermis of the skin to the epithelium of the oral mucosa. Note 

 well the character of the epithelium upon the two sides of the lip, 

 and the presence of hairs on the dermal side. Study the section 

 also for the structure of the skin, the layers, glands, etc. As illus- 

 trating the structure of the lip, note the striated muscle, connective 

 tissue, nerves and blood vessels and their arrangement. 



152. Lip. Horse or calf. Assigned for study. Transection. 

 ; collodion ; sections //. Stained with 



Compare this preparation with 151, recognizing the features enume- 

 rated above. Note the greater development of the hair of the skin. 



NAII,. 



153. Finger. Child. Transection through the tip. 



frozen section ( 61). Now in water. Stain with hydrochloric 

 acid carmine minutes ( 87), and counter-stain slightly with 



picric alcohol. 



This preparation illustrates : (#) the structure of the nail, () 

 the skin (of the finger). Note well the structure of the nail and the 

 nail-bed with its longitudinal corrugations cut across ; the relation 

 of nail and nail-bed to the skin of the finger. In addition there are 

 illustrated the structure of Pacinian corpuscles and sweat glands. 



HAIR. 



154. Hair. Homo. Assigned for study. Section of scalp, 

 cutting the hairs at right angles. ; paraffin ; stained with 

 hematoxylin, picrofuchsin, and methyl green. 



Since the section cuts the hairs at right angles and the hairs are 

 oblique to the surface, there appear transections of hairs at different 

 levels. Study carefully the sections of hair, identifying the layers 

 composing the hair and follicle at different levels, especially compar- 

 ing sections through the mouth of the follicle, through the middle of 

 the root, and through the hair bulb. Study the structure of the 

 sebaceous glands, their relation to the hair follicle and the point at 

 which they open. 



155. Hair. Homo. Demonstration. Section of scalp, cut 

 longitudinally with the hair showing the entire length. Note care- 

 fully the root of the hair, the follicle and its relation to the epider- 

 mis, the sebaceous glands and the hair muscle. 



