134 SPECIAL HISTOLOGY. 



of many series of -cells. The excavation commences in the 

 common biliary duct, proceeds towards its branches, and must 

 be considered to take place exactly as in other glands, i. e. 

 either by solution of the inner cells of the rudimentary struc- 

 tures, or by the excretion of a fluid between them and the 

 consequent production of a cavity. In this mode of regarding 

 the matter, there is only one point for consideration; viz. 

 that according to Remak, all the hepatic columns, even the 

 largest, form anastomoses, whilst, as is well known, the biliary 

 ducts ramify without anastomosing. The only solution of this 

 difficulty, consists in assuming that the anastomoses of the 

 primary, largest hepatic columns do not continue in the course 

 of the further development, but that they are re-absorbed, a 

 process which has its analogue in many phenomena of foetal 

 growth. In Man alone might we find an exception, for it seems 

 to me that the anastomoses of the right and left hepatic duct, 

 in the fossa hepatis, described by E. H. Weber, are perfectly 

 well explained by Remak' s observations, and are simply the 

 embryonic anastomoses of the rudiments of these canals, which 

 have attained to some, though no very great development. 

 The mode of origin of the fibrous membranes of the biliary 

 ducts becomes readily comprehensible, if we reflect how the 

 networks of hepatic columns and the fibrous layers of the liver 

 interdigitate ; so that layers of connective tissue, &c, might be 

 readily formed around the hepatic cylinders from those 

 elements of the fibrous layer which are nearest to them. The 

 further development of the vessels, nerves, &c, presents no 

 difficulties, taking place in the same way as in other organs. 

 The gall-bladder in the Chick, according to Remak, is a process, 

 at first solid, of one hepatic duct, which subsequently becomes 

 hollow and rapidly increases in size. I saw the folds of its 

 mucous membrane, as early as in the fifth month, in a human 

 foetus. 1 



1 [In his last memoir (Philosophical Transactions, 1853), Dr. Handfield Jones 

 maintains that, in Fishes, Amphibia, and Birds, the liver is developed independently 

 of the intestine, and, that the first rudiment of the excretory apparatus is the gall 

 bladder, whence ducts extend on the one hand into the intestine, and on the other 

 into the liver. He has not traced the development of the liver in Mammalia. 



Vogt, however (Embryogenie des Saumons, p. 175), states that in Coregonus 

 palea, the liver is at first a rounded, solid mass of cells, in contact with a diverticulum 



