1894.] MICROSCOPICAL JOURNAL. 141 



a mucli slighter area to the fluids in the spaces of the 

 surrounding tissues, than do the alveolar cells, they stain 

 more deeply and are much smaller in gross size. These 

 facts lead one to suspect that the cells of the duct have 

 much less of the work of the gland to perform than do 

 those of the alveolus. If we take as our conception of 

 the work of a gland-cell, that it receives materials from 

 the blood which it transforms chemically into some form 

 of product, and which it throws out into the lumen thence 

 to find its way into the mouth cavity, w^e readily see that 

 it is equally suitable that the active alveolar cell should 

 show a large front to the blood as its pyramidal shape 

 admirably fits it to do, while the duct should expose an 

 equally small area as it does by reason of its very small 

 base and tall columnar form. 



J. — -— ^:s» endothelium Sections of the sali- 



r\ ••• r^-; ■• ; <© vary gland, as in fact 



Capillary -sheath.. ^^ ^^ ^^^ alimentary 



, tissues, give good op- 



-nucleu* in ' ° ^ ^ 



endothelium^ portunities for this 

 •QQiia.. surface^'. , , study of the structure 



— muscle 1 ayer '' 



Artery in view of arterioles and capil- 



optical section, from parotid gland, i . t ^ j • 



lanes. In studying 

 the former, one of the smallest of the arterioles should 

 be selected, in a place as free from other objects as possi- 

 ble. The microscope should be then carefully focussed, 

 at one time on the surface, and at another on the centre 

 of the tube, so as to obtain an optical section. In the sur- 

 face view the unstriped muscle cells are visible clasping 

 the tube, in some of these the cell is seen full length on 

 the top of the tube, in others a part is seen on top, the 

 rest being on the other side. In the centres of these cells 

 the nucleus is clearly seen. The nucleus is recognizable 

 by its deeper stain. Underneath the muscular coat can 

 be seen other nuclei, which run in a transverse direction, 

 these are the nuclei of the cells which form the inner 



