152 ELEMENTARY BIOLOGY. [CHAP. 



a. Examine with a low power. 



a. Note the numerous uri7iiferous tubuies of which 

 the organ is mainly composed ; they twist about 

 in several directions, and are consequently cut, 

 some transversely, some obliquely, and others 

 more or less longitudinally. The latter are most 

 conspicuous at the outer (convex) border. 



/?. The clear round spaces, scattered about ; these 

 are sections of Malpighian capsules. Some may 

 be seen to lodge a granular mass (^glomerulus). 



b. Examine with a higher power — 



a. The epitJieliuvi of the tubules ; composed for the 

 most part of a single layer of large squarish 

 cells, each with a large round deep-staining 

 nucleus. 



y8. The epithelium of the capsules ; flattened and 

 squamous, its nuclei well defined, seen to be 

 reflected over the glomeruli (i.e. the latter are 

 outside it). Look for sections showing the con- 

 nection of tubules with capsules. ^ 



y. Blood capillaries ; scattered among the tubules, 

 conspicuous in borax-carmine preparations by 

 the refractive deep-staining nuclei of the red 

 corpuscles (cf § i8. b. y). 



c. Compare sections of the fresh kidney treated with 

 silver nitrate, as directed at § 2. c. Examine under 

 a high power. 



a. The capsules. The boundary lines of their epi- 

 thelial cells will be distinctly seen; they are 

 those of a tesselated epithelium. 



