310 THE CAUSES OF THE xi 



they all come under the same condition. Every 

 one of these microscopic filaments and fibres (I 

 now speak merely of the general character of the 

 whole process) every one of these parts could 

 be traced down to some modification of a tissue 

 which can be readily divided into little particles of 

 fleshy matter, of that substance which is composed 

 of the chemical elements, carbon, hydrogen, oxygen, 

 and nitrogen, having such a shape as this (Fig. 2). 

 These particles, into which all primitive tissues 

 break up, are called cells. If I were to make a 

 section of a piece of the skin of my 

 hand, I should find that it was 

 made up of these cells. If I 

 examine the fibres which form the 

 various organs of all living animals, 

 I should find that all of them, at 

 one time or other, had been formed 

 out of a substance consisting of similar elements ; 

 so that you see, just as we reduced the whole body 

 in the gross to that sort of simple expression given 

 in Fig. 1, so we may reduce the whole of the 

 microscopic structural elements to a form of even 

 greater simplicity ; just as the plan of the whole 

 body may be so represented in a sense (Fig. 1), so 

 the primary structure of every tissue may be 

 represented by a mass of cells (Fig. 2). 



Having thus, in this sort of general way, 

 sketched to you what I may call, perhaps, the 

 architecture of the body of the horse (what we 



