THE ALIMENTARY CANAL AND ITS APPENDAGES 179 
(ante, p. 43), ze. the structural variation of the first rib, and the feeble respiratory 
activity and consequent slight movement of the tips of the lungs. I consider that 
these phenomena should be regarded as degenerative, on the assumption that the 
remote ancestors of Man were still provided with cervical ribs, and that their lungs 
extended farther towards the head than they now do. There must thus, as I think, 
have been effected in the Phylogeny of Man first a shifting of the respiratory organs 
in a caudal direction, and next in order the formation of the diaphragm, and, in 
connection with the latter, a modification of the respiratory mechanism originally 
restricted to the lungs and the walls of the thorax. The contrast between this 
theory and that of Hasse is obvious, and although I am as little able as he is to 
furnish proofs, I believe that my explanation receives support from the facts of 
development and Comparative Anatomy. 
