Page:Popular Science Monthly Volume 46.djvu/102

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is but very feebly represented in man. "Padding" accounts for all the rest—a little more or less of fat and cellular tissue.

"Every face however full,
Padded round with flesh and fat,
Is but modeled on a skull,"

and it tells the same tale of the rest of the figure. It seems an odd statement at first sight, but there are many millions of beings who have an outside instead of an inside skeleton. What a miserable existence these poor creatures must have if they have a good figure, for it can not be exhibited! The lobster is of the 40-exoskeleton type.

I have dealt with necks, now for the other extreme. It might be argued that one great difference between ourselves and the rest of the vertebrates is marked by the fact of our having no tail. We all have tails. 'Tis true they are wretched specimens, but they exist universally. We do not wag our tails, but only the other day I spoke with a gentleman who had a dog whose caudal vertebræ were anchylosed together. A little careful selection with this dog, and it is probable that a race of dogs might be developed with an os coccygis like ourselves. Disuse invariably leads to abortion. The little mass of anchylosed vertebræ that we call the OS coccyx is our best apology for a tail, but this region of the spinal column becomes wonderfully modified and developed if we compare it with its homologue in other members of the creation. It may act as a hand, may be the exclusive locomotive organ, it may contain the only free vertebræ in the body. In the spider monkey it is prehensile and is often used as a hand. In some sharks the number of the vertebræ amounts to two hundred and seventy. In tortoises the coccygeal vertebræ are the only free vertebræ. In the sole the neural spines and the hypophyses are remarkably developed. Finally, the bone may be even more rudimentary than in man. In the bat there are but two coccygeal vertebræ.

Quite a developed tail has, says Marshall, been discovered in the human race in certain rare and anomalous cases.

In the embryonic stage of the vertebrates the spinal column is represented by the so-called notochord, and this notochord is temporarily represented in the Ascidians, a class of animals bearing not the remotest resemblance to the Vertebrates. This is a highly interesting fact in connection with the interrelation of species.

One other most interesting fact: At an early period of our development—that is to say, at an early part of our embryo existence—the os coccyx is free and projects beyond the lower extremities.

One other less interesting fact: What tail we have is always carried between our legs—no doubt, in the majority of instances, there is good reason for it!