U-shaped section of the intestine following immediately on the stomach. Being fixed down behind the abdominal cavity it cannot be further convoluted, and this accounts for Galen's description of it. It is about twelve fingers' breadth long in the animals dissected by Herophilus. [87] Galen, περι ανατομικων εγχειρησεων {peri anatomikôn encheirêseôn}, _On anatomical preparations_, ix. 5 (last sentence). [88] Galen, περι φλεβων και αρτηριων ανατομης {peri phlebôn kai artêriôn anatomês}, _On the anatomy of veins and arteries_, i. Erasistratus, the slightly younger Alexandrian contemporary of Herophilus, has the credit of further anatomical discoveries. He described correctly the action of the epiglottis in preventing the entrance of food and drink into the windpipe during the act of swallowing, he saw the lacteal vessels in the mesentery, and pursued further the anatomy of the brain. He improved on the anatomy of the heart, and described the auriculo-ventricular valves and their mode of closure. He distinguished clearly the motor and sensory nerves. He seems to have adopted a definitely experimental attitude--a very rare thing among ancient physicians--and a description of an experiment made by him has recently been recovered. 'If', he says, 'you take an animal, a bird, for example, and keep it for a time in a jar without giving it food and then weigh it together with its excreta you will find that there is a considerable loss of weight.'[89] The experiment is a simple one, but it was about nineteen hundred years before a modern professor, Sanctorio Santorio (1561-1636), thought of repeating it.[90] [89] The quotation is from chapter xxxiii, line 44 of the _Anonymus Londinensis_. H. Diels, _Anonymus Londinensis_ in the _Supplementum Aristotelicum_, vol. iii, pars 1, Berlin, 1893. [90] Sanctorio Santorio, _Oratio in archilyceo patavino anno 1612 habita; de medicina statica aphorismi_. Venice, 1614.