174 DR. E. KLEIN. 



the branched cells and the nerve fibres in their finest 

 ramifications. 



These examples can be multiplied from every book or 

 journal of the present day containing papers on animal 

 histology. 



What I Avish to point out is that a structure that is very 

 indistinctly or perhaps not at all discernible in the perfectly 

 fresh statCj but becomes very sharp and well marked after a 

 particular reagent, need not necessarily be an artificial pro- 

 duct; if this same structure can be shown also with other 

 reagents, although not so well defined, we are quite justified, 

 I think, in regarding it as preformed, and not as an artificial 

 product. 



Now, as regards the intranuclear network. What I described 

 in Part I of my paper, chiefly with the aid of chromate of 

 ammonia, coincides with what is possible to make out in the 

 fresh state, and after other reagents (see my Part I, p. 3£1), 

 e. g. MilUer's fluid, bichromate of potash, osmic acid, spirit, 

 &c., with this difference, that in the specimens prepared 

 successfully with chromate of ammonia, there are here some- 

 times failures on account of the elements swelling up and 

 becoming quite transparent, but the appearances are infinitely 

 more regular and much better defined than with other 

 reagents. 



The exquisitely beautiful honey- combed network in the 

 nuclei of the endothelial and connective-tissue cells in the 

 mesentery of newt, prepared successfully with 5 per cent, 

 chromate of ammonia, the rich branching, the minute 

 structure of these cells, and of the unstriped muscle fibres, are 

 brought out with a clearness and delicacy not reached by 

 any other reagent with which I have treated that membrane. 



The observations which I have recorded in the present 

 Part II prove the correctness of the deductions stated in 

 Part I as regards the structure of cells and nuclei. In study- 

 ing the epithelial and gland-cells of mammals, besides examin- 

 ing them in the fresh state, I have had occasion to compare 

 the appearances obtained by the use of different reagents, as 

 stated in the foregoing pages — and because the appearances 

 were found similar or identical they were accepted as denot- 

 ing a preformed structure. If one appearance is brought out 

 "with greater distinctness with chromic acid than with another 

 reagent, I do as Professor Flemming does, viz. I give it the 

 preference in the examination, but I should not reject spirit, 

 chromate of ammonia, bichromate of potash, &c., if in any 

 other instances the appearances are better defined by one of 



