GREGORY, QUADRUPEDAL LOCOMOTION 269 



Cope neglected to follow up the important mechanical and adaptive 

 corollaries of these facts. He merely drew the very questionable infer- 

 ence that "those elements which receive the principal impact in progres- 

 sion are those which increase in length [in phylogeny] " 10 



In his paper on "The Angulation of the Limbs of Proboscidia, Dino- 

 cerata, and other Quadrupeds, in Adaptation to Weight," Osborn 11 con- 

 cluded that 



u The straightening of the limb [in the Dinocerata, Proboscidia, etc.] is an 

 adaptation designed to transmit the increasing weight through a vertical shaft. 

 Correlated with it are the shifting of the facets into the direct line of pressure 

 and the alteration of their planes from an oblique to a right or horizontal 

 angle with relation to the vertical shaft." 



Gaudry, 12 in describing the limbs of extinct South American ungu- 

 lates, endeavored to show how the pose of these animals could be inferred 

 from a study of the facets, — an idea which had been previously advanced 

 by Osborn. 13 Gaudry also designated as "rectigrade" the pose of ele- 

 phants and similar heavy forms which stand with straightened limbs and 

 toes, resting the weight chiefly on the pad. 



The marked contrasts in the limbs and musculature between the slow- 

 moving heavy-bodied ungulates and the slender swift-footed or cursorial 

 types in various phyla, constitute a subject which will be discussed 

 in considerable detail in the monograph on the Titanotheres by Professor 

 Osborn. At his suggestion, the following notes, forming a part of the 

 present writer's studies on this subject, are now published, together with 

 some of the drawings which have been made by Mr. Erwin S. Christman, 

 under the direction of the writer, for the monograph above mentioned. 

 The writer is also indebted to Dr. W. D. Matthew for valuable criticisms 

 and suggestions. 



Limbs regarded as Compound Levers 



The simple principle that the limbs of quadrupeds are compound levers 

 and that the relative lengths of the upper, middle and lower segments 

 are adapted to specific loads, muscular powers and speeds, although well 

 understood by students of human and equine locomotion, has apparently 

 not hitherto been applied to elucidate the adaptive contrasts between 

 cursorial and "graviportal" 14 ungulates. 



10 Loc cit. 



"Am. Nat, vol. xxxiv, pp. 89-94. 1900. 



12 "Fossiles de Patagonie. Les Attitudes de quelques Animaux." Ann. de Paleon- 

 tologie, tomei. 



w . "Patrlofelis and Oxysena restudied as Terrestrial Creodonts. - ' Bull. Amer. Mus. Nat. 

 Hist.. Vol. 13, pp. 270, 271. 1900. 



11 This word has been invented by Professor Osborn to describe the conditions in 

 heavy-bodied animals with long proximal and short distal limb segments. 



