However, intelligence is one thing, life another, and the spinal cord, with its supply of nerve-substance, doubtless looked after the mere mechanical functions of life; and while even the spinal cord is in many cases quite small, in some places, particularly in the sacral region, it is subject to considerable enlargement. This is notably true of Stegosaurus, where the sacral enlargement is twenty times the bulk of the puny brain--a fact noted by Professor Marsh, and seized upon by the newspapers, which announced that he had discovered a Dinosaur with a brain in its pelvis. In their great variety of size and shape the Dinosaurs form an interesting parallel with the Marsupials of Australia. For just as these are, as it were, an epitome of the class of mammals, mimicking the herbivores, carnivores, rodents and even monkeys, so there are carnivorous and herbivorous Dinosaurs--Dinosaurs that dwelt on land and others that habitually resided in the water, those that walked upright and those that crawled about on all fours; and, while there are no hints that any possessed the power of flight, some members of the group are very bird-like in form and structure, so much so that it has been thought that the two may have had a common ancestry. The smallest of the Dinosaurs whose acquaintance we have made were little larger than chickens; the largest claim the distinction of being the largest known quadrupeds that have walked the face of the earth, the giants not only of their day, but of all time, before whose huge frames the bones of the Mammoth, that familiar byword for all things great, seem slight. For Brontosaurus, the Thunder Lizard, beneath whose mighty tread the earth shook, and his kindred were from 40 to 60 feet long and 10 to 14 feet high, their thigh bones measuring 5 to 6 feet in length, being the largest single bones known to us, while some of the vertebrae were 4-1/2 feet high, exceeding in dimensions those of a whale. [Illustration: Fig. 19--A Hind Leg of the Great Brontosaurus, the Largest of the Dinosaurs.] The group to which Brontosaurus belongs, including Diplodocus and Morosaurus, is distinguished by a large, though rather short, body, very long neck and tail, and, for the size of the animal, a very small head. In fact, the head was so small and, in the case of Diplodocus, so poorly provided with teeth that it must have been quite a task, or a long-continued pleasure, according to the state of its digestive apparatus, for the animal to have eaten its daily meal. [Illustration: Fig. 20.--A Single Vertebra of Brontosaurus.] An elephant weighing 5 tons eats 100 pounds of hay and 25 pounds of grain for his day's ration; but, as this food is in a comparatively concentrated form, it would require at least twice this weight of green fodder.