OBSERVATIONS ON STRUCTURE OF CELLS AND NUCLEI. 321 



work so clearly as when seen from the surface. The net- 

 work appears more delicate in the nuclei of the gland-cells 

 and endothelial plates of the mucosa than in those of the 

 epithelial cells of the surface. 



In some nuclei the ground substance, in which is embedded 

 theintranuclear network, appears slightly tinged red, in others 

 it is perfectly colourless. 



Such are the appearances presented by the nuclei of the 

 surface-epithelium, of the gland-cells, and of the endothelial 

 plates of the mucosa of the stomach, prepared simply in 5 per 

 cent, solution of chromate of ammonia. Of the greatest 

 clearness and distinction, and of greater preference as regards 

 preservation in microscopic specimens that are permanently 

 to be sealed up, are the nuclei of the above cellular elements, 

 if, after having been kept for about twenty-four hours in 5 per 

 cent, solution of chromate of ammonia, the stomach is placed 

 for about I — 1 hour in a mixture of 2 parts of l-6th per 

 cent, solution of chromic acid and 1 part of methylated 

 alcohol — a mixture which I am in the habit of using with 

 great advantage for hardening glandular organs, and such as 

 contain connective- and muscular tissues — then washed and 

 treated as above. 



But also by keeping the fresh stomach for twenty-four 

 hours in Miiller's fluid, washing and then staining it in picro- 

 carmine, the intranuclear network may be perceived in some 

 nuclei, although with far less distinctness than after the 

 above methods. In many nuclei the network is too much 

 shrunk and presents, therefore, the well-known ' granular ' 

 appearance. The aj)pearance is somewhat, though not very 

 much, improved by placing the stomach, after Miiller's fluid 

 and before washing it, in the above mixture of chromic acid 

 and spirit for about | — 1 hour. 



The nuclei examined in the perfectly fresh condition 

 show distinctly, although faintly, part of the intra- 

 nuclear network, a good magnifying power, as Zeiss^s F or 

 Hartnack's Imm. 10, and good light, as that reflected by Avliite 

 clouds, being indispensable. Other reagents, as osmic acid, 

 alcohol, chromic acid, bichromate of potash, give not very 

 satisfactory results, although osmic acid and bichromate of 

 potash show the intranuclear network in some instances more 

 or less distinctly. 



Measurements which I made of the nuclei in specimens 

 prepared after the 5 per cent, chromate of ammonia method 

 and mounted in glycerine, give the following numbers as the 

 mean : 



