190 MANUAL OF HISTOLOGY. 



cells are bound together by a colloid substance, although this 

 is a point which has not yet been definitely settled. 



Sections of a dog's liver, immersed for a short time in dilute osmic acid, will 

 occasionally exhibit a brown or black tracing between adjoining cells. Pres- 

 sure on the cover glass will part them and leave the darkened material free in 

 the field of vision. I have satisfied myself that this tracing is not of a nerve, 

 biliary duct, or connective-tissue fibril ; it is either a portion of the boundary 

 layer of a liver-cell, or, as I suppose, a colloid substance between two cells. 

 This appearance, however, is not constant. 



The protoplasm is of a dark brownish or greenish color. It 

 is viscid, and contains numerous granules of small size, in ad- 

 dition to smaller or larger fat-droplets. 1 In livers hardened by 

 chromic acid or alcohol, the shrinkage of the cells causes them 

 to appear polyhedral, and they also seem much darker than in 

 the fresh state. If the portal or hepatic vein has been injected, 

 the cells will show distinct indentations produced by the dis- 

 tended capillaries. 



When liver-cells are treated with diluted acetic acid, their 

 protoplasm becomes pale, while their nuclei are rendered more 

 conspicuous. In a dilute solution of caustic potassa the cells 

 swell up, become rounded, and are finally dissolved. With 

 water they also swell up, become paler and more rounded, and 

 at length disintegrate. In the fresh state, by the addition of 

 an indifferent fluid ( per cent, solution of chloride of sodium, 

 or iodized serum), the liver-cells are said to show protoplasmic 

 movements. The granular substance of the liver-cells has 

 been shown (by Schiff, in frogs, and by Nasse, in certain mam- 

 malia) to consist of an animal amylum, which is converted into 

 sugar through the agency of a peculiar ferment. 



The fat-droplets may be either small in number and size or 

 quite numerous and large. Not infrequently they coalesce to 

 form larger fat-globules. In the so-called fatty infiltration they 

 are very large, and compose the greater part of the cells. The 

 nuclei are granular, and where two or more of them occupy 

 the same cell, they may apparently be united to each other. 



1 According to Kupffer and Klein the substance of the cells is composed of a 

 honeycombed network, i.e., an intracellular reticulum. Klein says the nucleus is lim- 

 ited by a thin membrane, and includes an intranuclear network, containing occa- 

 sionally one or two nucleoli. The intranuclear network is in continuity with the 

 intracellular one, and the network of contiguous cells are in connection with one 

 another (Klein and Smith : Atlas of Histology). 



