1906.] Liver Cells to the Blood-vessels and Lymphatics. 487 



investing fibres which are finer in texture and surround the blood and lymph 

 spaces. The radial fibres are the thicker and coarser of the two sets. 



Mall (43) described similar appearances in the lobules after removal of the 

 liver cells by artificial pancreatic digestion. The nature of the fibres is 

 uncertain. Kupffer states that they have the appearance of elastic fibres, but 

 cannot certainly be classified as such, as they are not stained with orcein. 

 Mall believed them to be elastic. Ebner (17) showed that in preparations 

 stained with orcein, fibres in the interlobular connective tissue, which are 

 undoubtedly elastic, take on a deep stain, while the " Gitterfasern " are 

 unaffected. He believes them to be composed of collagen, and classifies 

 them as fine white connective-tissue fibrils. 



In 1900 Minot (45) described a hitherto unrecognised form of blood 

 circulation without capillaries in the organs of vertebrata. Among other 

 organs the liver is one in which, according to Minot, the blood-vessels of the 

 lobules are not true capillaries, but blood spaces or " sinusoids." He states 

 that a sinusoid differs from a capillary in that its wall consists of an endo- 

 thelial or endotheloid layer without any strengthening addition of adventitia 

 or media. It is of relatively large size ; its epithelium is closely fitted 

 against the cells of the organ in which the sinusoid is developed, and it has 

 numerous wide and frequent communications with the neighbouring sinusoids 

 of the organ, while a capillary follows its own shape and is chiefly or wholly 

 embedded in connective tissue. A sinusoid, on the other hand, has little 

 or no connective tissue between it and the adjacent parenchyma, and in 

 those cases where this occurs it is a secondary or late acquisition, and the 

 amount remains usually, perhaps always, very small. The development 

 of capillaries and sinusoids differs. Minot states that a capillary arises 

 from pre-existing vessels or from vaso-formative cells, and is an addition 

 by new histogenesis to vessels previously differentiated, while a sinusoid, 

 on the contrary, is not the product of a new histogenesis, but results 

 from ingrowth of the endothelial wall of a pre-existing blood-vessel. In 

 the development of the liver the hepatic cylinders grow into and subdivide 

 the portal vein, the endothelial cells retaining their embryonic character, 

 and being closely applied to the ingrowing columns of liver cells. The blood- 

 vessels or sinusoids between the columns have irregular shapes and numerous 

 connections with one another, and are typically many times wider than 

 capillaries. Minot states that in the liver the sinusoids come to resemble 

 capillaries by secondary change, and may be called " capilliform sinusoids." 

 The fine fibres of connective tissue he believes to be a secondary development, 

 but one that does not change the essential intimate relation of the wall of the 

 sinusoid to the adjacent parenchyma. 



VOL. lxxviii. — B. 2 



