Page:Popular Science Monthly Volume 71.djvu/477

Rh No. 3, b, and we see presently an accumulation of cells which is assuming a definite form, No. 4, b, that in the next figure has clearly become the promise or beginning of a new terminal joint, Fig. 60. The minute study of this process has shown that the regeneration depends practically exclusively upon the cells of the young type, and that after they have grown out and accumulated here in this manner, No. 3, b, some of them undergo differentiation, becoming muscle cells; others change in the manner indicated here, where we see a commencing alteration of the nuclei, which is further accented in Fig. 60, and leads to such a grouping of the cells that the glands, which were originally present there, are also reproduced. The regenerative process, then, clearly illustrates to us from another point of view the great importance of the young type of cells.

This completes the evidence which my time permits me to lay before you in order to convince you that really the young type of cells is physiologically and functionally important, that it really does possess the power of growth such as I have attributed to it.

We will pass now to another part of our subject, with which the lecture will close. Age represents the result of a progressive cytomorphosis. We have learned that of cytomorphosis death is the end, the culmination. It is a necessary result of the modification and change of structure which goes on in every individual of our species and of all the higher animals. We are familiar with the death of cells. It occurs constantly and, as I have endeavored to explain to you, it plays a great part in life. It promotes the performance of various functions which are of advantage to the body as a whole, which could not be accomplished without the death of some cells. But the death which we have in mind when we speak ordinarily of death is something different from this. It is the death of the whole. But even the death of the whole has its strange complications. A great deal of our knowledge of the functioning of the body is due to the fact that the parts do not die when, as we commonly say, the body as a whole, the individual, is dead. The organ is alive and well. One