OBSERVxVTIONS ON STRUCTURE OF CELLS AND NUCLEI. 163 



that in a liver — hardened in 80 per cent, of methylated spirit, 

 or in our mixture of chromic acid and methylated spirit, — 

 obtained from a dog killed either after having been kept without 

 food for twenty-four hours or one hour after taking its food, the 

 liver cells show a more open network, i. e. the interstitial sub- 

 stance is present in a greater amount, than if the liver be 

 taken of an animal that had been killed five or six hours after 

 partaking of a meal, in which case the cells appear more uni- 

 formly " granular," i. e. the network closer and the interstitial 

 substance less abundant. 



The nucleus of the liver cells is spherical, and contains a 

 uniform network. Some nuclei show a regular layer of peripheral 

 circular fibrils mentioned on a former page. Spirit preparations 

 often reveal in this network one or more central or eccentric 

 large dots — nucleoli; in some livers, hardened in strong spirit, 

 there is hardly a liver cell that does not possess a nucleolus, 

 but in other livers, hardened in 80 per cent of spirit or in 

 chromic acid, I see only few liver cells whose nucleus possesses a 

 necleolus. 



For this reason alone it cannot be regarded as an important 

 element. When examining carefully with a high power (Hart- 

 nack, immersion 10) a series of nuclei which contain what would 

 generally pass for a " characteristic, large and bright nucleolus," 

 I find that twice out of three times I can see that it is a complex 

 structure, and traceable to a part of the intranuclear network 

 having shrivelled up. But besides the small bright dots due to 

 optical sections of fibrils, there are undoubtedly larger particles 

 in some intranuclear networks, but these are smaller than the 

 above " characteristic " nucleoli. 



In the nuclei of liver cells that show the intracellular network 

 with open meshes, e. (j. the liver of guinea-pigs injected with % 

 per cent of Berlin blue, the intranuclear network does not contain 

 as a rule any traces of larger particles ; it is a uniform network 

 and anatomoses with the former by a great many radiating 

 branchlets. I do not agree with Kupfer, according to whom the 

 network is most cons])icuous around the nucleus, for in those 

 instances in which I find the network in its greatest distinctness 

 and beauty (see guinea-pig^s liver treated as above stated), I see 

 that it pervades the substance of theliver cells in an uniform manner. 

 In some instances of the injected guinea-pig's liver I have seen this 

 network assume a faint blue tint on that part of the cell 

 that is next to a capillary vessel, but I presume this is due to an 

 imbibition of the network with the Berlin blue. In many places 

 the network of one cell is seen in direct connection with that of the 

 neighbouring cells. 



In conclusion, I wish to mention an appearance which I have 



