[54] The rediscovery and verification of this and other Aristotelian observations is detailed by C. Singer, ‘Greek Biology and the Rise of Modern Biology,’ _Studies in the History and Method of Science_, vol. ii, Oxford, 1921. Passing from his general ideas on the nature and division of living creatures we may turn to some of the most noteworthy of his actual observations. In the realm of comparative anatomy proper we may instance that of the stomach of ruminants. He must have dissected these animals, for he gives a clear and correct account of the four chambers. ‘Animals’, he says, ‘present diversities in the structure of their stomachs. Of the viviparous quadrupeds, such of the horned animals as are not equally furnished with teeth in both jaws are furnished with four such chambers. These animals are those that are said to chew the cud. In these animals the oesophagus extends from the mouth downwards along the lung, from the midriff to the _big stomach_ [_rumen_, or paunch], and this stomach is rough inside and semi-partitional. And connected with it near to the entry of the oesophagus is what is called the _kekryphalos_ [_reticulum_, or honeycomb bag]; for outside it is like the stomach, but inside it resembles a netted cap; and the kekryphalos is a good deal smaller than the _big stomach_.’ The term _kekryphalos_ was applied to the net that women wore over their hair to keep it in order. ‘Connected with this kekryphalos,’ he continues, ‘is the _echinos_ [_psalterium_, or _manyplies_], rough inside and laminated, and of about the same size as the kekryphalos. Next after this comes what is called the _enystron_ [_abomasum_], larger and longer than the echinos, furnished inside with numerous folds or ridges, large and smooth. After all this comes the gut....’[55] ‘All animals that have horns, the sheep for instance, the ox, the goat, the deer and the like, have these several stomachs.... The several cavities receive the food one from the other in succession: the first taking the unreduced substances, the second the same when somewhat reduced, the third when reduction is complete, and the fourth when the whole has become a smooth pulp....’[56] ‘Such is the stomach of those quadrupeds that are horned and have an unsymmetrical dentition (μὴ ἀμφώδοντα); and these animals differ one from another in the shape and size of the parts, and in the fact of the oesophagus reaching the stomach central-wise in some cases and sideways in others. Animals that are furnished equally with teeth in both jaws (ἀμφώδοντα) have one stomach; as man, the pig, the dog, the bear, the lion, the wolf.’[57] [55] _Historia animalium_, ii. 17; 507ᵅ 33. [56] _De partibus animalium_, ii. 17; 507ᵇ 12. [57] _Historia animalium_, ii. 17; 507ᵇ 12.