496 POPULAR SCIENCE MONTHLY 



means confined to plants; it occurs equally in ourselves all the time; 

 at every period of our life we have been getting through with some por- 

 tion of our body; that portion acquired a certain organization, it 

 worked for us awhile, and then being done with it, we threw it away 

 because it was dead. Very early in the history of every individual 

 there was a production of blood, and then followed the destruction of 

 some of the blood corpuscles and their remains were used for various 

 purposes. The pigment which is in the liver comes from the destroyed 

 blood corpuscles, and it is believed that the pigment which colors the 

 hair is derived from the same source. The blood corpuscles contain 

 a material which when chemically elaborated reappears as the deposit 

 which imparts to the hairs their coloration. You, of course, are all 

 familiar with the loss of hair. It occurs to everybody, but did you 

 ever think that it means that the hair which has lived has died, and 

 that that hair which was a part of you has been cast off ? That is what 

 the loss of hair means to the biologist — the death of a part and the 

 throwing away of it, and it is typical of what is going on through the 

 body all the time. It occurs in the intestines, where the elements 

 which serve for purposes of digestion are continually dying and being 

 cast off. The outer skin is constantly falling off and being renewed, 

 and that which goes is dead. In every part of the body we can find 

 something which is dying. Death is an accompaniment of develop- 

 ment; parts of us are passing off from the limbo of the living all the 

 time, and the maintenance of the life of each individual of us depends 

 partially upon the continual death going on in minute fragments of 

 our body here and there. 



Our next step in this course of lectures will carry us into the micro- 

 scopic world, and with the aid of the lantern at the next lecture I shall 

 hope to demonstrate to you a little of the microscopic structure of the 

 body and of the general nature of the change, which exhibits itself 

 in the body from its earliest to its latest condition. With such knowl- 

 ege in our minds, we shall be able next to study some of the laws of 

 growth. We shall gain from our microscopic information a deeper 

 insight into some of the secrets of the changes, which age produces in 

 the human bodv. 



