The laws and mechanics of circulation, with the principle involved in animal movement . oordinated through the medulla oblon-gata, whirls it over the road-bed in the vascular lines with suchexpedition as to make the journey within a minute from thecavity of the stomach. But all plain enough in the light of thelaw that applies and automatism in the tissues, the muscularand nervous forces swelling at the difficult points for compellingthe passage and completing the circuit; otherwise is utterlyinexplicable. There is more ! In all the expanse of venous territory inthe portal system, not a valve p
The laws and mechanics of circulation, with the principle involved in animal movement . oordinated through the medulla oblon-gata, whirls it over the road-bed in the vascular lines with suchexpedition as to make the journey within a minute from thecavity of the stomach. But all plain enough in the light of thelaw that applies and automatism in the tissues, the muscularand nervous forces swelling at the difficult points for compellingthe passage and completing the circuit; otherwise is utterlyinexplicable. There is more ! In all the expanse of venous territory inthe portal system, not a valve presents. Why ( The answeris not far to seek. The presence of a valve in the portal veinwould prevent reflux, so that congestion of the liver could ABSENCE OF VALVES IN THE POKTaL SYSTEM. 237 not find relief in copious transudations in the intestiual canal,producing diarrhoea, thereby conserving liver-structure, which,is the object of this arrangement, and would inevitablyend in disaster. Indeed, we have example of this in thepartial constrictions which occur in the liver from hyper-. Fig. 90.—Portal System in Diagram.—Gray. The transverse colon is removed, the-duodenum divided near the pyloric orifice and the stomach pulled aside, in order toexpose the vena portse, with the mesenteric arteries omitted, for better definition ofthe mesenteric veins. plasia of connective tissue produced by alcohol, interferingwith the course of the blood through the liver, tending todam it back in the portal system, leading to diarrhoea in the cavity of the abdomen, producing the drunk-ards dropsy. But with valves in the veins, this reflux could-not occur, and life would have a speedy termination, clos- 238 ABSENCE OF VALVES IN THE PORTA L SYSTEM. ing upon it, sharp and terrible as the jaws of a mastodon. Itis well, then, for the drunkard that there are not valves in theportal vein; while temporary congestions of the liver arepassed over and never known, finding prompt relief in
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