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.
Another discovery of recent times which has a no less important bearing on the question raised by this chapter is the now ascertained fact that many of these parasitic diseases are common to both animals and men, and may be communicated from the former to the latter. All are familiar with the fact that the smallpox, in a modified and mild form, is a disease of cattle as well as of men, and we avail ourselves of this fact in the practice of vaccination. Scarcely less familiar is the communication of the parasitic trichinæ, which often infest the flesh of swine, to those who eat such meat. And research is constantly extending the number of such diseases. Turkeys, we are now told, have the diphtheria, and may communicate it to men; men also sometimes take from horses the loathsome disease known as the glanders. Now in the light of such facts as these, it is plain that an ideal dietary law would, as far as possible, exclude from human food all animals which, under given conditions, might be especially liable to these parasitic diseases, and which, if their flesh should be eaten, might thus become a frequent medium of communicating them to men.
Now it is a most remarkable and significant fact that the tendency of the most recent investigations of this subject has been to show that the prohibitions and permissions of the Mosaic law concerning food, as we have them in this chapter, become apparently explicable in view of the above facts. Not to refer to other authorities, among the latest competent testimonies on this subject is that of Dr. Noel Gueneau de Mussy, in a paper presented to the Paris Academy of Medicine in 1885, in which he is quoted as saying: "There is so close a connection between the thinking being and the living organism in man, so intimate a solidarity between moral and material interests, and the useful is so constantly and so necessarily in harmony with the good, that these two elements cannot be separated in hygiene.... It is this combination which has exercised so great an influence on the preservation of the Israelites, despite the very unfavourable external circumstances in which they have been placed.... The idea of parasitic and infectious maladies, which has conquered so great a position in modern pathology, appears to have greatly occupied the mind of Moses, and to have dominated all his hygienic rules. He excludes from Hebrew dietary _animals particularly liable to parasites_; and as it is in the blood that the germs or spores of infectious disease circulate, he orders that they must be drained of their blood before serving for food."