Internally the muscular layers are lined by an epithelium.
For pharmaceutical purposes crude petroleum is no longer generally used by civilized races, though the product vaseline is largely employed in this way, and emulsions of petroleum have been administered internally in various pectoral complaints; while the volatile product termed rhigolene has been largely used as a local anaesthetic.
"She's bleeding internally," she said.
Potassium nitrate was used at one time in many different diseased conditions, but it is now never administered internally, as its extremely depressant action upon the heart is not compensated for by any useful properties which are not possessed by many other drugs.
The walls, both internally and externally, are encrusted with marbles.