92

ELEMENTS OF MATERIA MEDICA.

colocynth , and elaterium. These, when swallowed in large doses, act asacrid poisons. They are employed as purgatives in torpid conditions ofthe bowels; as hydragogues in dropsical affections, and as counter-irritants in affections of the brain. They are objectionable remedies ininflammatory and irritable conditions of the alimentary canal.

e. The fifth group contains the mercurial purgatives; as the hydrar-gyrum cum creta, the pilula hydrargyri, and calomel. We employ theseas alterative purgatives, and to promote the hepatic functions. Asthey are uncertain in their operation, they are usually combined with,or followed by, other purgatives.

7. Cholagogues. —These are medicines which increase the evacuationof bile. It is probable that most, if not all, drastic purgatives increase thesecretion and excretion both of bile and pancreatic juice, by irritating theopening of the ductus choledochus in the duodenum, just as certain sub-stances taken into the mouth provoke an increased discharge of salivaby irritating the mouths of the salivary ducts. Graaf (quoted by Barbier,Traite Element, de Mat. Med. tom. iii. p. 125, ed. 2nde) says, that if apurgative be administered to a dog, and when it is beginning to operatethe abdomen be laid open, the bile and pancreatic juice will be observedflowing into the duodenum.

When we consider the peculiarities attending the hepatic circulation,and that all the remedial agents whose particles are absorbed have topass through the portal vein,—the vein by whose branches the bile issecreted,—our astonishment is great that this secretion is not more fre-quently affected by the various me-dicinal agents put into the stomach.I have already' mentioned (p. 15)the different substances which havebeen detected in the blood of eitherthe portal vein, or of veins (splenicand mesenteric) opening into it. Thebranches of this vein which ramifybetween the lobules of which the

Fig. 28.

liver is principally made up, are de-nominated by Mr. Kieman {Philos.Trans, for 1833) interlobular veins:their minuter ramifications withinthe lobules are called lobular venous

Representing the interlobular branches of the ’ and these last inosculate

portal vein , the lobular venous plexuses, towards the centre with the mtralo-and the intralobular branches of the he- bular ramules of the hepatic veins.patic veins of three lobules.

a a a. The interlobular veins contained in the spaces.

bbb. The interlobular veins which occupy the fissures, and which, with the veins inthe spaces, form venous circles around the lobules. This is the appearance which the '}venous circles present when examined with a common magnifying glass; they are, 1however, formed by numerous, and not by single, branches, as represented in the figure! jccc. The lobular venous plexuses, the branches of which, communicating with each ;■other by intermediate vessels, terminate in the intralobular veins. The circular andovoid spaces, seen between the branches of the plexuses, are occupied by portions of \the biliary plexuses, constituting the acini of Malpighi . j

ddd. The intralobular branches of the hepatic veins, in which the vessels of the fplexuses terminate.