Some of the animals and birds prohibited were probably, then, animals eaten in connection with idolatrous feasts by the neighbouring heathen. Isa. lxv. 4 shows that swine's flesh was eaten at sacrificial meals by idolaters, and from the expression "broth of abominable things is in their vessels" it is clear that the flesh of other animals was so used. All these would necessarily be prohibited to Israel; but beyond a few, such as the swine, which was sacrificed to Tammuz or Adonis, and the mouse and the wild ass, we have no means of knowing what they were. That this is a _vera causa_ of such prohibitions is shown by the facts mentioned by Professor Robertson Smith, that "Simeon Stylites forbade his Saracen converts to eat the flesh of the camel, which was the chief element in the sacrificial meals of the Arabs, and our own prejudice against the use of horse-flesh is a relic of an old ecclesiastical prohibition framed at the time when the eating of such food was an act of worship to Odin." The very ancient and stringent prohibition of blood as an article of diet is probably to be accounted for in this way also. Blood was eaten at heathen sacrificial feasts; without other reason that would be sufficient. These are the general lines which must have determined the list of clean animals in the view of the lawgiver, since he brings them in under the head of idolatry and under the two general grounds we have discussed (p. 289, _supra_). Jewish writers, however, especially since Maimonides, have regarded these prohibitions as aiming primarily at sanitary ends, and as a proof of their efficacy have adduced the unusually high average health of the Jews, and their almost complete exemption from certain classes of disease. No such point of view is suggested in the Scriptures themselves, for it would surely be rather farfetched to class possible disease as an infringement of the holiness demanded of Israel, or as a thing unworthy of Yahweh's sons. Nevertheless a general view of the list of clean animals here given would support the idea that sanitary considerations also had _something_ to do with the classification. The practical effect of the rule laid down is to exclude all the _carnivora_ among quadrupeds, and so far as we can interpret the nomenclature, the _raptores_ among birds.[80] "Amongst fish, those which were allowed contain unquestionably the most wholesome varieties." Further, the nations of antiquity which developed such categories of clean and unclean animals seem in the main to have taken the same line. The ground of this probably is the natural disgust with which unclean feeders are always regarded. Animals and birds especially which feed, or may be supposed to feed, on carrion, are everywhere disliked, and as a rule they are unsuitable for food. Grass-eating animals, on the other hand, are always regarded as clean. Scaleless fish, too, are generally more or less slimy to the touch, and with them reptiles are altogether forbidden.