1890.J Study of the Vertebrate Liver. 65 



In addition to these two sets of passages an intracellular branched 

 system of lacuna may be described as forming the rootlets of the 

 canaliculi. These spaces open directly into the canaliculi, and have 

 been previously partly described by Pfliiger and Kupffer. 



Description of a True, Secretory, or Primary Lobule. From what 

 precedes it follows that the liver tubes, instead of being grouped 

 round the terminal hepatic veins, are distinctly arranged in small 

 pyramidal masses, which correspond to the lobules of other glands. These 

 lobules are composed of the tubules diverging from the intermediate 

 tubes found in the portal line of divergence, each set of intermediate 

 tubes opening into a terminal bile duct. An arrangement somewhat 

 analogous had already (in 1882) been supposed to exist by Sabourin, 

 but he had been unable to discover in healthy livers what he believed 

 to exist and had been obliged to fall back upon diagrammatic repre- 

 sentations which are not altogether correct. 



Development of the Liver. Eberth and other observers since have 

 recognised that the embryonic liver is composed of hypoblastic tubes 

 branching in a mass of mesoblast. This being common to the liver 

 and all other glands does not explain the differences between these 

 organs. Between the third and sixth weeks of embryonic life (in 

 man) nearly the whole of the mesoblastic tissue separating the hypo- 

 blastic columns becomes transformed into embryonic veins full of 

 blood. In other glands only a small part of that tissue becomes 

 transformed into veins, the greater part remaining in the shape of 

 interlobular and interlobar tissue. In the liver, therefore, the 

 hepatic veins take the place of the greater part of the stroma of 

 other glands. 



It is only around the oldest hypoblastic tubes which become ulti- 

 mately ducts, and at the periphery of the organ, that a little meso- 

 blastic tissue becomes transformed into fibrous connective tissue 

 (Grlisson's capsule). 



Structure of the Hepatic Cells. The mitoma gives unmistakable 

 evidence of a further differentiation of parts of the trabeculae com- 

 posing it. These trabeculae are contractile. 



The paramitoma is enclosed in the meshes formed by the mitoma, 

 and is the chief seat of the anabolic and katabolic changes taking 

 place in protoplasma. The products thus formed probably under the 

 influence of the mitoma accumulate in the midst of the paramitoma ; 

 when soluble, they permeate it ; when insoluble, they are precipitated 

 in the shape of drops or vacuoles, globules, granules, crystals. For 

 these products only the name of Paraplasma should be reserved. 



In the paraplasma two kinds of elements may be recognised, 

 namely : (1) those resulting from the katabolic process of the cell 

 or other tissues (kataplasma), e.g., bile pigment; (2) those result- 

 ing from the anabolic processes (anaplasma), e.g., glycogen. In the 



VOL. XLIX. y 



