4 THE ENGINES OF THE HUMAN BODY 



spinal column, and the bones of the arm and leg work 

 just as in life. Then we fitted out the skeleton with 

 muscles, the structures or engines which move the bones 

 in walking, breathing, and eating, and which make up 

 the soft parts or flesh of the body. We also provided 

 this cardboard Goliath with a heart or blood-pump ; 

 arteries by which the heart could pump the blood out- 

 wards, and veins designed to bring the blood back to the 

 heart, were also provided and set in place. A windpipe 

 or trachea was fitted to bring air from the nose to the 

 lungs, which were duly placed within the chest. A 

 mouth, tongue, jaws, teeth, oesophagus, stomach, and 

 intestines were fitted into their proper places. Goliath 

 was given a brain, a spinal cord, and a full set of nerves. 

 He was given eyes, ears, and a nose, and then, to make 

 him quite complete and comfortable, a covering of skin. 

 We foresaw that even in such a Goliath the heart, brain, 

 eye, ear, stomach, caecum and appendix, the joints of his 

 hands and of his feet were on too small a scale to be seen 

 by those who were in the galleries or distant seats of the 

 great theatre. So we made very big models of these 

 parts, and contrived them in such a way that they could 

 be dissected and thus be taken to pieces. By this means 

 the manner in which small parts of the human machine 

 worked could be seen and understood by those who did 

 not come early enough to get a front seat. Then, too, 

 in order to make it quite clear that the machinery of the 

 human body does work on the same plan as that of the 

 machines which engineers turn out, we had to make large 

 working models of the small engine — an internal-com- 

 bustion engine — which drives a motor cycle, for, as we 

 shall see, the human machine is furnished with many 

 motor engines, only we call them muscles — not engines. 

 We had to make models of various kinds of pumps, of 

 bellows, of telephone exchanges, and of many other con- 

 trivances and inventions. And so it came about that 

 when the children and the "grown-ups" crowded into 

 the spacious, brightly lighted theatre of the Royal In- 

 stitution on the afternoons of that Christmas season they 



