PKOGBESS OF MICROSCOPICAL SCIENCE. 



135 



membranes possess, beneath the suiDerficial epithelium, a single layer 

 of flat cells, consisting of protojilasm and united with each other by a 

 very delicate intercellular substance. If a portion of small fresh in- 

 testine be deprived of its epithelium, and impregnated with solution 

 of nitrate of silver, there apjjears a beautiful network of more or 

 less sinuous dark lines on the surface of the villa, exactly like that 

 on the surface of the serous membranes. A similar endothelium 

 makes its appearance beneath the epithelium of the Lieberkiihnian 

 glands of the intestine, so that the membrana proj^ria of the gland 

 is a mere endothelial membrane. [V. Czerny foimd in silver- 

 stained preparations some years ago, that the membrana propria of 

 the sweat-glands of the skin consists of endothelial plates.] In 

 the bronchi, a similar layer of subepithelial endothelium is to be 

 found ; it consists of polygonal plates, which in silver-stained prepara- 

 tions are bordered by straight lines. Deboue believes it probable that 

 the epithelium of the bronchi does not continue into the infundibula, 

 but that the cellular lining of these latter is a continuation of the 

 above-mentioned endothelium. The subepithelial endothelium of the 

 mucous membrane of the bladder consists of very large polyhedral 

 cells, bordered by straight lines. From all this, says Dr. Klein, it 

 appears that the subepithelial endothelium corresponds to what has 

 been very often described as a structureless basement membrane. 



The Mesolving and Penetrating Power of certain Objectives. — Profes- 

 sor Ardissone publishes in the ' New Italian Journal of Botany,' the 

 following Tables showing the relative resolving and penetrating power 

 of objectives by four different French and German makers. In the 

 determination of the separating or resolxdng power he employs the 

 diatoms ordinarily used as test-objects, and for the reason that they 

 are more generally accessible than Nobert's Test-plates. In publish- 

 ing these Tables, Professor Ardissone does not intend to pronounce a 

 judgment upon the relative value of the work of the different makers. 

 He very justly states that the separating or resolving capacity is only 

 one of the qualities of a good objective. The same is also true of the 

 quality of penetration. In the Table, N. refers to Nacliet, G. to Gund- 

 lach, H. to HartnacTc, and Z. to Zeiss. 



