368 



Rev. H. N. Hutchinson — Observations on 



inward curve, like a bow set up, so that its convex side points 

 towards the posterior end of the animal. Fig. 5 shows the articulation 

 proposed by the writer. 



The position of the fore-limb is mechanically impossible ! Such 

 a bow would collapse under the strain put upon it. 



It is important to bear in mind that this curvature is all in one 

 plane, a vertical plane. There is no foreshortening or any bulging 

 out at an angle to the body as in modern reptiles. Now this must 

 be wrong. We will return to this matter later on. It is difficult, 

 one might almost say impossible, to conceive that such a bone was 

 intended to be used for movements in a direction AB and CD parallel 

 with the major axis of the skeleton, as in mammals, as indicated in 

 the diagram Fig. 8, p. 369. 



Fig. 5, fore-Hmb (after author) ; Figs. 6, 7, two views of humerus of Diplodocus. 



As already pointed out, that inward curve of the humerus makes it 

 weak. Hatcher put it the other way about. But no bone intended to 

 work in such a manner would be so thin in the direction at right 

 angles to its movements. They are always thick in the direction in 

 which they are used. It must be wrong mechanically. Compare 

 the humerus of a dog, or rhinoceros, elephant, etc. They all have 

 a rounder shape which gives them the necessary strength for move- 

 ments in the directions AB and CD in a vertical plane, or, in other 

 words, in directions at right angles to its major axis. Now this is 

 just the direction in which the humerus is thinnest. 



Kow compare this arrangement with the posture adopted in our 

 restoration. The humerus now works something like an oar. Fig. 9 



