Multaque per sudorem ex alto pressa feruntur,
Multa per os exhalantur, quam languida anhelant:
His igitur rebus rarescit corpus; et omnis
Subruitur natura dolor quam consequitur rem.
Propterea capitur cibus, ut suffulceat artus,
Et recreat vires interdatus, atque patentem
Per membra ac venas ut amorem obturet edendi.”
(De Rerum Nat. iv, 856.)
The explanation given by one of Rhases’ authorities is to the same effect. He says: “Since our bodies are in a continual state of waste from the surrounding atmosphere, and the innate heat which is within, it behoved them to have nourishment to supply the part which is melted down; and, as all the food which is taken is not assimilated, it was necessary that there should be passages for the discharge of the superfluities.”
Hippocrates, Aristotle, Galen, and Musonius (ap. Stobæi Sentent. 18) remark that the stomach is to animals what the earth is to vegetables.