COMMENTARY. The ancient writers on Dietetics are, Hippocrates (de Diæta, de Affectionibus, et alibi); Celsus (ii); Dioscorides (Mat. Med. ii); Galen (de Facult. Alim., et de Probis Pravisque Aliment. Suc.); Xenocrates (de Aliment, ex aquat.); Oribasius (Med. Collect. i et seq.); Aëtius (ii); Simeon Seth (de Alimentis); Actuarius (de Spiritu Animali, p. ii); Anonymus (Tract, ap. Ermerins Anecdota Græca); Marcellus (Sideta de Piscibus); Psellus (Carmen de Re Medica); Rhases (ad Mansor. iii, Cont. xxxiii); Avicenna (Cantic. p. ii); Averrhoes (Comment. de Cantic); Haly Abbas (Theor. v, 15); Athenæus (Deipnos. passim); Plutarch (de Sanitate tuenda, Symposiacon); Macrobius (Saturnal. vii); Cælius Apicius (de Opsoniis); Geoponica (xii); Horace and Martial (pluries.) Of all the ancient writers on Dietetics, Galen is beyond dispute the best. In the two treatises mentioned above, he has treated of everything connected with this subject so fully and so correctly, as to leave little to be supplied even at the present day. All the subsequent authorities in general are his servile copyists, with the exception of Averrhoes, who commonly differs from him only by deviating into error. The ancient philosophers were at great pains to explain why a regular supply of food is necessary to the existence of animals. On this subject, Timæus Locrus, Plato, and Aristotle have philosophized with great acuteness and ingenuity. No one, however, has given a plainer account of the matter than the poet Lucretius in the following verses: “Illud item non est mirandum, corporis ipsa Quod natura cibum quærit quoiusque animantis; Quippe etenim fluere, atque recedere corpora rebus Multa modis multis docui, sed plurima debent Ex animalibus iis, quæ sunt exercita motu; 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.