But while this view has been elaborated with great ability and skill, it yet fails to account for all the facts. It is quite overlooked that if the reason of the prohibition of carnivorous birds and quadrupeds is to be found in the fact that they live by the destruction of life, the same reason should have led to the prohibition of all fishes without exception, as in Egypt; inasmuch as those which have fins and scales, no less than others, live by preying on other living creatures. On the other hand, by the same principle, all insects which derive their sustenance from the vegetable world should have been permitted as food, instead of one order only of these. Where so much learning and profound thought has been expended in vain, one might well hesitate to venture anything in exposition of so difficult a subject, and rest content, as some have, with declaring that the whole subject is utterly inexplicable. And yet the world advances in knowledge, and we are therefore able to approach the subject with some advantage in this respect over earlier generations. And in the light of the most recent investigations, we believe it highly probable that the chief principle determining the laws of this chapter will be found in the region of hygiene and sanitation, as relating, in this instance, to diet, and to the treatment of that which is dead. And this in view of the following considerations. It is of much significance to note, in the first place, that a large part of the animals which are forbidden as food are unclean feeders. It is a well-ascertained fact that even the cleanest animal, if its food be unclean, becomes dangerous to health if its flesh be eaten. The flesh of a cow which has drunk water contaminated with typhoid germs, if eaten, especially if insufficiently cooked, may communicate typhoid fever to him who eats it. It is true, indeed, that not all animals that are prohibited are unclean in their food; but the fact remains that, on the other hand, among those which are allowed is to be found no animal whose ordinary habits of life, especially in respect of food, are unclean. But, in the second place, an animal which is not unclean in its habits may yet be dangerous for food, if it be, for any reason, specially liable to disease. One of the greatest discoveries of modern science is the fact that a large number of diseases to which animals are liable are due to the presence of low forms of parasitic life. To such diseases those which are unclean in their feeding will be especially exposed, while none will perhaps be found wholly exempt.