174 



NORMAL ANATOMY OF THE LIVER. 



the gall-bladder, which are large and form a 

 remarkable plexus, enter the glands in the 

 right border of the lesser omentum ; and those 

 from the left lobe converge to the lymphatic 

 glands situated along the lesser curve of the 

 stomach. 



The nerves which supply the liver are de- 

 rived from the systems both of animal and 

 organic life ; the former are filaments of the 

 right phrenic and two pneumo-gastric nerves, 

 and the latter of the solar plexus. The branches 

 from the right phrenic nerve descend by the side 

 of the inferior cava, to unite with the hepatic 

 plexus in the right border of the lesser omen- 

 tum. Swan describes a small ganglion, to 

 which filaments converge from the right semi- 

 lunar ganglion and right phrenic nerve, as being 

 the medium of communication between the 

 phrenic nerve and the hepatic plexus. The 

 branches of the pneumo-gastric nerves pass 

 between the two layers of the lesser omentum 

 to its right border, and pursuing the course 

 of the hepatic artery are distributed with 

 the hepatic plexus to the gall-bladder and 

 along the portal canals. The hepatic plexus 

 proceeds from the solar plexus and surrounds 

 the hepatic artery to the transverse fissure; its 

 filaments then accompany the branches of that 

 vessel to their ultimate termination, and some 

 few are observed to ramify upon the portal 

 vein. 



Progressive development of the liver in the 

 animal series. The liver in its simplest condi- 

 tion is a mere inflection of the mucous lining 

 of the alimentary canal, forming a small coecal 

 recess or follicle. The capillary vessels rami- 

 fying upon the parietes of this follicle pour 

 their secretion upon its internal surface, and it 

 is thence conveyed to the alimentary canal to 

 be mingled with the ingesta. In this its most 

 rudimentary form the liver would appear to be 

 present in the Laginellu, a small cilio-brachiate 

 polypus described and figured by Dr. Arthur 

 Farre.* Upon the stomach of the Luginella 

 are seen several minute cosca which open into 

 its cavity ; they are usually empty when the 

 animal has been for some time without food, 

 but become filled with a brownish fluid after a 

 meal. The next most elementary form of the 

 hepatic ccocum is seen in the single lengthened 

 follicle discovered by Owen in the ascar-is ha- 

 licoris. This follicle opens into the alimentary 

 canal at about one-third from its oral extremity. 

 Among the Annelida, as in the medicinal leech 

 (fig. 69, vol. i.) the liver is represented by 

 numerous simple ccecal pouches appended to 

 each side of the digestive canal. The next 

 step in the complication of the organ is ob- 

 served in the lengthened filiform tubuli which 

 are connected with the sides of the canal in the 

 Aphrodita. These are narrow and constricted 

 at their commencement, dilating gradually as 

 they proceed farther from the intestine, and 

 terminating by a small oval sac. In other 

 species of the same genus and in the Areni- 

 cola (Jig. 70, vol. i.) they display a tendency 

 to ramify, by developing small ccecal pouches 



* Philosophical Transactions, 1837. 



from their sides. In these terminal sacculi 

 Pallas discovered a " bitter fluid, of an olive- 

 brown or greenish-black colour," which he 

 conceived to be the juices of marine plants 

 which had gained admission into the tubuli 

 through their openings of communication with 

 the intestine, but which, it is more than pro- 

 bable, was the proper biliary secretion of the 

 tubes themselves. In the class Inxccta the 

 hepatic cceca vary in progressive development 

 from the simple vesicular dilatations observed 

 upon the digestive canal of the Lampyrus 

 splendidula, or the simple ccecal tubulus of the 

 carnivorous Cicindela, to the numerous ccecal 

 follicles of the Dytiscus, or to the more length- 

 ened tubuli of the Blatta orientalis. Through- 

 out the whole of the class the character of the 

 liver is tubular, the development and extent of 

 the tubuli depending upon peculiarities in the 

 food or habits of the animals. In Arachnida, 

 the ccecal follicles are short, and terminate 

 at their extremities in a cluster of numerous 

 rounded vesicles, which give to the organ a 

 lobulated appearance. They are seen in the 

 Scorpion, in Jig. 83, c, c, page 204, vol. i. 

 In the class Crustacea, the hepatic organ assumes 

 a higher and more complicated character; the 

 simple ccecal follicle of Insecta becomes 

 branched and ramified, of which we have a 

 good example in the Argulus foliaceus, deli- 

 neated by Miiller. In the Astacus fluviatilis 

 (Jig- 214, page 483, vol. i.) the hepatic fol- 

 licle is more branched than in the Argulus ; 

 and in the Pagurus striatus (Jig. 215, page 484, 

 vol. i.) the liver is composed of an extraordinary 

 assemblage of ramified follicles. In the hepatic 

 organ of the Squilla mantis we perceive a remark- 

 able transition from the simple branched and ra- 

 mified follicle of the lower Crustacea to the higher 

 forms of the organ in the molluscous classes. 

 Upon the exterior it is lobulated, and each 

 lobe is composed of a congeries of minor lo- 

 bules which appear like granulations upon its 

 surface. Examined in its interior it presents a 

 primary dilated sac of considerable size, from 

 which branch off a number of secondary sacs 

 of smaller dimensions, and these latter are 

 studded over every part of their surface with 

 minute crecal follicles of a rounded form. In 

 the subregnum Molluxa the liver is of large 

 size, and approaches in external form to the 

 solid and lobulated organ of vertebrata. In 

 internal conformation we may still trace among 

 the lower classes a close analogy with the rami- 

 fied tubuli of Articulata. Thus in the class 

 Gasteropoda the gland is composed of coBcal 

 pouches, which divide and subdivide into 

 smaller and smaller follicles and terminate in 

 small dilated sacs. They may be compared 

 in their disposition to the stem, branches, 

 twigs, and fruit of a cluster of grapes. A 

 liver of this kind is seen in the Helix pomatia. 

 In the Murex triton the follicular structure of 

 the organ would appear to be lost. The ex- 

 ternal surface presents a lobulated form, but 

 the interior is composed of a delicate spongy 

 tissue, consisting of larger and smaller cells, 

 which may all be inflated from the excretory 

 duct. This seeming difference in the structure 



