452 



SECRETION. 



to two and a half times the diameter of the 

 secreting cells. The tubes of one lobule are 

 distinct from those of the neighbouring lobuli, 

 or only communicate indirectly by means of 

 the trunks or hepatic ducts, originating from 

 the tubes, and lying in the interspaces of the 

 lobuli. The secreting cells (fig. 320.) are irre- 

 gularly angular or polygonal in form, from 

 mutual pressure, and line the interior surface 

 of the tubes. They vary in size in a moderate 

 degree in different animals, and also in the 

 same animal, appearing to depend upon cer- 

 tain conditions of the animal and liver."* 

 We have ourselves verified these important 

 observations to a certain point, not having 

 been able to obtain a view of the regular and 

 complete plexus of ducts figured and described 

 by Dr. Leidy,but having satisfied ourselves that 

 a system of canals, prolonged from the bile- 

 ducts, exists in each lobule. The recently 

 published observations of Dr.Natalis Guillot-j- 

 are to the same effect. He has not been able, 

 any more than ourselves, to distinguish mem- 

 branous parietes around these canals ; and he 

 considers that they are simply channelled out 

 in the parenchyma of the liver, the particles 

 of which form its sole borders. It appears 

 probable to us, however, that these canals 

 correspond to the spaces left in the centre of 

 the biliary tubuli of insects, &c. ; and that the 

 membranous walls, if they exist at all, would 

 be found to invest the cells which immediately 

 bound these passages. 



The biliary cells of the Mammalia (fig. 320.) 

 usually contain a certain number of adipose 

 particles; their size and number, however, 

 vary considerably according to the food of 

 the animal, the amount of exercise which it 

 has been taking, and other circumstances. 

 If an animal be very fat or well fed, especi- 



Fig. 320. 



Hepatic cells of human Liver. 



a, three secreting cells of ordinary aspect; I, a 

 secreting cell much more highly magnified, show- 

 ing the central nucleus, granular particles, and 

 oil globules ; c, four secreting cells from a human 

 liver in a state of fatty degeneration, showing a 

 great increase of oil globules. (After Leidy.} 



ally with farinaceous or oleaginous substances, 

 the proportion of adipose particles is much 

 greater than in an animal moderately fed and 

 taking much exercise. The size of the glo- 

 bules varies from that of mere points, scarcely 

 distinguishable from the granular contents of 

 the ceils but by their intense blackness, up to 

 one-fourth of the diameter of the cell. The 

 finely granular matter is the portion from 

 which the colour of the cell is derived ; it 

 seems to fill the space not occupied by the 

 oil globules ; and it often obscures the nu- 

 cleus, so that the latter cannot be distinguished 

 until acetic acid is added, which makes the 

 granular matter more transparent without 

 affecting the nucleus. 



The following are the dimensions of the 

 hepatic cells in various animals, according to 

 the measurements of Dr. Leidy (loc. cit.). 



* 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 possible, and to examine this slice when restored 

 to its original condition by moisture. 



f Annales des Sciences Naturelles, Mars, 1848. 



