Royal Society. 227 



distinct vessel conveying a different kind of blood is distributed to 

 the hepatic duct, as soon as the liver assumes the parenchymal form, 

 it seems probable that the mode in which the secreted bile is con- 

 veyed out of the organ, is by its permeating the coats of the minute 

 ducts in obedience to an endosmotic attraction, which takes place 

 between the bile in which the ducts may be said to be bathed, and 

 a denser (perhaps mucous) fluid formed in their interior. The 

 large quantity of oily matter frequently existing in a free state in 

 the secreting parenchyma of the liver, which must be regarded as a 

 product of secretory action, seems to suggest the idea, that a cer- 

 tain quantity of the biliary secretion may be directly absorbed into 

 the blood, and in this manner conveyed away from the organs, just 

 as occurs in the thyroid body, suprarenal capsules, and other 

 glands unprovided with efferent ducts. 



With respect to the development of the liver, the author considers 

 the opinion of Reichart to be decidedly the correct one, namely, 

 that its formation commences by a cellular growth from the germi- 

 nal membrane, independently of any protrusion of the intestinal 

 canal. On the morning of the fifth day, the oesophagus and stomach 

 are clearly discernible, the liver lying between the heart, which is in 

 front, and the stomach which is behind ; it is manifestly a parenchy- 

 mal mass, and its border is quite distinct and separate from the digest- 

 ive canal ; at this period, the vitelline duct is wide, it does not open 

 into the abdominal cavity, but its canal is continued into an anterior 

 and posterior division, which are tubes of homogeneous membrane, 

 filled, like the duct, with opaque oily contents ; the anterior one 

 runs forwards, and forms behind the liver a terminal expanded 

 cavity, from which then passes one offset, which, gradually dilating, 

 opens into the stomach; a second, which runs in a direction up- 

 wards and backwards, and forms apparently a caecal prolongation ; 

 and a third and fourth, which are of smaller size, arise from the 

 anterior part of the cavity and run to the liver, though they cannot 

 be seen to ramify in its substance ; at a somewhat later period, these 

 offsets waste away, excepting the one which is continued into the 

 stomach, and then the mass of the liver is completely free and un- 

 connected with any part of the intestine. As the vitelline duct 

 contracts, the anterior and posterior prolongations of it become 

 fairly continuous and form a loop of intestine, the posterior division 

 being evidently destined to form the cloaca and lower part of the 

 canal. The final development of the hepatic duct takes place about 

 the ninth day by a growth proceeding from the liver itself, and 

 Consisting of exactly similar material ; this growth extends towards 

 the lower part of the loop of duodenum, which is now distinct, and 

 appears to blend with the coats of the intestine ; around it, at its 

 lower part, the structure of the pancreas is seen to be in process of 

 formation. The further progress of development of the hepatic 

 duct will, the author thinks, require to be carefully examined, but 

 the details he has given in this paper have satisfied him of the cor- 

 rectness of the statement that the structure of the liver is essentially 

 parenchymal. 



Q2 



