66 PRACTICAL HISTOLOGY. 



the lips to detach some epithelial scales ; then place a large 

 drop of saliva on a slide, skim off the air-bubbles with a 

 needle ; cover, and examine. 



a. Squamous epithelial cells, single or cohering together 

 in groups, will be found scattered throughout the field. 

 Observe their shape, large size (30-50 //,), the nucleus 

 usually single and oval. 



The epithelium of the mouth is stratified. The cells 

 under examination belong to the most superficial layers. 



b. Salivary corpuscles will be found singly or in clusters. 

 Size, rather larger than that of a mucous corpuscle. Observe 

 the Brownian motion of the granules between the nucleus 

 and the envelope. There is no amoeboid movement. 



c. Mucin. Place a drop of magenta at the margin of 

 the cover-glass, and elevate it slightly to allow the dye to 

 penetrate the viscous fluid. The nuclei of the epithelium 

 and salivary corpuscles become brilliantly stained, and 

 very delicate films or fibrils of precipitated mucin will 

 probably be found stretching here and there across the 

 field. The mucin is precipitated by the alcohol in the 

 magenta fluid, and as it is slightly stained by the dye it 

 may be found without much difficulty. Acetic acid may 

 be used to precipitate the mucin, but the films being 

 colourless are, in that case, much more difficult to 

 find. 



87. V. S. skin" of palmar surface of finger hardened 

 first in chromic acid and spirit ( 16). The skin may be im- 

 bedded in paraffin, as described in 300, and held in the hand 

 during section ; or it may be imbedded in paraffin and cut 

 in a microtome, as described in 303 ; or, best of all, it 

 may be frozen, and cut in the freezing microtome, as de- 

 scribed in 305. However obtained, the section must be 

 extremely thin. If the slice be large and difficult to spread 

 out on the slide, put in a tumbler or beaker full of water. 

 Before it has had time to sink to the bottom thrust the 

 slide into the water, and with the aid of a needle draw the 

 section upon the centre of the slide, with the epidermic 

 surface facing the broad margin of the slide. Dry the 

 slide with a cloth or bibulous paper close up to the tissue. 



