The mere size of these extinct reptiles is a very natural cause of wonder and admiration. At the same time, it is well to remember that the body of the largest African elephant is as big, or very nearly as big, as the body of the biggest of these extinct reptiles. Some of these giant extinct reptiles had very long tails and necks, which the elephant cannot boast. No extinct animal is known which approaches in bulk the great whales of various kinds at present inhabiting the sea. The striking thing about many huge extinct animals is that they are represented to-day by similarly constructed animals of much smaller size. Thus we know giant extinct sloths, which contrast strangely with the small living sloths of to-day, giant extinct rat-like animals and giant extinct kangaroos far exceeding the bulk of living rats and kangaroos. But it is distinctly not true that all recent animals are degenerate and small as compared with extinct related kinds. The modern horse is far larger than its extinct ancestors, which we can trace back in a gradual diminishing series to a little beast no bigger than a spaniel. So, too, the earliest elephants known are quite small creatures. The interesting point about extinct animals is really not so much that they were often large of their kind, but that they are often of kinds quite unknown at the present day among living animals. On the other hand sometimes (but by no means always) they can be shown to be connected as ancestors to living animals by a series of intermediate forms. The remains of the connecting forms are found embedded in successive rock-strata, intermediate in age between the present day and the remote period when the earliest members of the series were alive and flourishing--and we can follow out in many instances (for example, in the pedigree of the horse, and again of the elephant) the gradual but very extensive changes by which the descendants of a long extinct kind of animal have been “transformed” into modern recent animals, familiar to us. 4. _Work at the Pasteur Institute_ Professor Elias Metschnikoff was busy, when I saw him at the Institut Pasteur in Paris last September, with an experimental investigation of “appendicitis.” He finds that chimpanzees can exhibit this disease, and he is led by experiments on those animals to believe that a gas-producing micro-organism--the bacillus aërogenicus--already known as occurring in the human intestine--is especially active in exciting the disease. Parasitic worms or other foreign bodies must first wound the delicate lining of the appendix before the virulent gas-forming bacillus can penetrate and start inflammation and abscess. Metschnikoff was also investigating a disease of tropical regions, known as “the Yaws.” Most people would imagine that this name refers to a disease like the gapes, but it is quite different, being an ulceration of the skin caused by a spirillum.