THE LOBULAR PARENCHYMA. 



109 



with considerable amplification, say X 400, and then only in the 

 thinnest portion of the sections. They are, properly speaking, merely 

 minute channels in the parenchyma, and have, it is believed, no wall. 



The hepatic cells are polyhedral, about twice the size of a white 

 blood-corpuscle, say one-one thousandth of an inch, usually with 

 a single nucleus and with granular protoplasm, frequently con- 

 taining minute fat droplets and granules of yellow pigment. The 

 existence of a definite limiting membrane has been questioned, as far 

 as the cell of human liver is concerned, although such structure can 

 be shown in many of the lower animals. 



The physiological plan of the intralobular structure is expressed in 

 the diagram, Fig. 78. The blood is brought into relation with the 

 lobular parenchyma the hepatic cells by the capillary plexus, and 



FIG. 78. DIAGRAM ILLUSTRATING THE INTRA-LOBULAR HISTOLOGY OF THE LIVER. 

 The hepatic cells are connected in columns between the blood capillaries. The cells are en- 

 dowed with the power of selecting, especially, such materials from the blood as are necessary 

 for the manufacture of bile. Having accomplished this, the secreted fluid is given up to the bile 

 capillaries, and by them poured into the ducts, and led out of the liver for subsequent use. The 

 direction of the pressure is indicated by the arrows. This is the histology of gland structures 

 generally. 



the elements necessary to constitute the bile are selected and carried 

 on, to be drained away by the bile capillaries and ducts. 



PRACTICAL DEMONSTRATION. 



It is best to begin with the liver from a pig. The amount of con- 

 nective tissue in the normal human liver is very small, and is mainly 

 confined to the support of the interlobular vessels; the boundaries of 

 the lobules are, therefore, poorly defined, and without the previous 

 observation of some well-outlined specimen, I find the student fre- 



