94 WHAT IS LIFE ? 



ci process which is absolutely marvellous, are formed 

 the cells (each of which has its nucleus and probably its 

 nucleolus) of which nearly the whole structure of the 

 living being, before birth and after birth, is composed. 



Yes, the human being is formed of these cells and the 

 molecular secretions or formations made by these cells. 1 

 They are always made of that which the human being 

 absorbs. Each cell is a living being. 2 



And now to continue the early alterations in the egg, 

 there comes another change on the scene. On the sur- 

 face of these membranes, the spherical mass, a thicken- 

 ing takes place, and in this a straight hollow groove 

 is formed, and this is the commencement of the brain 

 and spinal cord. The whole mass ultimately wraps 

 itself into a complex, somewhat cylindrical mass closed 

 at each end. " The human embryo," as the incipient 

 human being is called, u passes through a stage in which 



it is the Wolffian body, which forms in the adult the essential parts 

 of the renal and generative organs of the kidney, testicle, and 

 ovary." (" AJI Introduction to Human Physiology," A. D. Waller, 

 M.D., F.R.S., 1896, p. 579.) 



1 In many cases these secretions act as a sort of cement or mortar 

 just as bricks are held together by mortar, so are cells held together 

 by a sort of " cement-material," which is secreted by the cells. (See 

 Quain's " Elements of Anatomy," vol. i. part 2, 1893, p. 172.) 



2 " No satisfactory progress can be made till the idea of highly- 

 organized living things as units had been set aside ; till it was 

 recognized that they were in reality organisms, each constituent 

 part of which had its special life. Ultimate analysis of higher 

 animals and plants brings us alike to the cell, and it is to these 

 single parts, the cells, which are to be regarded as the factors of 

 existence. . . In a medical school, where the teaching is almost 

 exclusively concerned with human beings, this sentence should be 

 written large : ' The organism is not an individual, but a social 

 mechanism.' " (The second Huxley Lecture, delivered by Prof. 

 E. Virchow, October 3rd, 1898.) 



