“…When Cohnheim (1901) demonstrated that intestinal juice was capable of hydrolysing peptones to amino acids, some early workers suggested that protein must be hydrolysed to amino acids before being absorbed. This hypothesis gained ground when all known free amino acids were detected in intestinal contents during protein absorption in vivo (Abderhalden & L a m p , 1912;Cohnheim, 1912Cohnheim, , 1913 and when studies in vivo showed that complete hydrolysates of protein (consisting of free amino acids) disappeared rapidly from the lumen of the small intestine (Cathcart & bathes, 1905;Abderhalden & London, 1910). When it was found that only amino acids could be isolated from the portal circulation during protein absorption (Abel et al 1913), the idea that protein was completely hydrolysed to amino acids within the intestinal lumen became the classical view of protein absorption (Verzar & MacDougall, 1936).…”