698 ON FORM AND MECHANICAL EFFICIENCY [ch. 



in Fig. 343, A, with its beuding-moment diagram (B) ; and it is 

 evident that, if we turn this diagram upside down, it will still be 

 illustrative, just as before, of the bending-moments from point 

 to point: for as yet it is merely a diagram, or graph, of relative 

 magnitudes. 



To either of these two stress diagrams, direct or inverted, we 

 may fit the design of the construction, as in Figs. 343, C and 344. 



nc 



T] 



Fi.o. 343. 



Fig. 344 



Now in different animals the amount and distribution of the 

 load differs so greatly that we can expect no single diagram, 

 drawn from the comparative anatomy of bridges, to apply equally 

 well to all the cases met with in the comparative anatomy of 

 quadrupeds; but nevertheless we have already gained an insight 

 into the general principles of "structural design" in the quad- 

 rupedal bridge. 



In our last diagram the upper member of the cantilever is under 



