586 



OF SECRETION AND EXCRETION. 



containing numerous secreting cells, and the only difference exists in the ar- 

 rangement, the free tubes of the lower animals becoming anastomosed on forming 



Fig. 155. 



Fig. 156. 



Fig. 155. Transverse section of a Lobule of the Human Liver, showing the reticular arrangement of 

 the Bile-ducts, with some of the hranches of the Hepatic Vein in the centre, and those of the Portal 

 System at the periphery. 



Fig. 156. A small portion of this section more highly magnified, showing the secreting cells within 

 the tubes. 



an intertexture ia the Vertebrata. The tubuli vary in size in an unimportant 

 degree in different animals, and also in the same animal, being generally from 



two to two and a half 



Fig. 157. times the diameter of 



the secreting cells. 

 The tubes of one lob- 

 ule are distinct from 

 those of the neighbor- 

 ing *lobuli, or only 

 communicate indirect- 

 ly by means of the 

 trunks of hepatic 

 ducts, originating from 

 the tubes, and lying 

 in the interspaces of 

 the lobuli. The se- 

 creting cells (Fig. 157, 

 B) are irregularly an- 

 gular or polygonal in 

 form, from mutual 

 pressure, and line the 

 interior surface of the 

 tubes. They vary in 

 size in a moderate de- 

 gree in different animals, and also in the same animal, appearing to depend upon 

 certain conditions of the animal and liver." 1 ' The subsequent observations of 

 Dr. Natalis Gruillot 3 are mainly to the same effect. He has not been able, how- 



1 See "American Journal of the Medical Sciences," Jan. 1848. Dr. Leidy does not 

 specify the mode in which his preparations have been made ; but we understand that his 

 plan is to dry a small portion of injected liver, then to make as thin a slice of this as pos- 

 sible, and to examine this slice when restored to its original condition by moisture. 



2 "Annales des Sciences Naturelles," Mars, 1848. 



A, portion of a Biliary Tithe, from Human Liver, with the secreting cells : 

 B, secreting cells detached, a, in their normal state, fc, a cell more highly 

 magnified, showing the nucleus and distinct oil-particles, c, in various stages 

 of fatty degeneration. 



