92 PRESENT-DAY RATIONALISM 



enormous, and if it took the form of a rope would 

 greatly impede it. 



" The most remarkable example of the penniform 

 muscle in Nature is the muscle which lifts the wing of 

 the bird. The bird's wing is depressed by great and 

 powerful muscles but it is lifted by a small compact 

 muscle. . . . The nature of a bird's flight is this : The 

 depressor muscles of the wing must be made enormously 

 great, to strike the air with the utmost force ; the muscles 

 which lift the wing must be made as light and small as 

 possible. Therefore we find that Nature always employs 

 the penniform muscle to lift a bird's wing. Thus no 

 force is lost and the bird is enabled to repeat the down- 

 ward stroke much faster than if the prismatic form of 

 muscle had been retained." 



Dr. Haughton concludes his lectures by describing 

 an " ellipsoid muscle that surrounds a cavity" — a muscu- 

 lar bag. "In attempting the solution of the problem of 

 an ellipsoid muscle, I found myself brought into contact 

 with a problem in architecture which has baffled archi- 

 tects for many years. I mean the problem of the 

 equilibrium of an elliptical dome. Every portion of 

 a curved ellipsoidal muscle forms a portion of a small 

 flat dome ; and to determine the equilibrium of tensions 

 and strains among the muscular fibres of such an animal 

 structure, is the same thing as solving the problem in 

 architecture of what are the strains in various directions 

 in an elliptical dome. The difficulty of constructing 

 equilibrated domes may be illustrated by the fact that, 

 with the exception of the Pantheon in Paris, there is not 

 a truly equilibrated dome in existence. The dome of St. 

 Paul's is braced up with double chains of iron, and other 

 chains of timber and lead put on to cover the defects in 

 the original structure of the dome. No case exists, I 



