36 MATERIALS FOR A MEMOIR ON 



investigation Prof. Horace Jayne extended many facilities. Mr. 

 Edwin A. Kelley has kindly furnished a carefully prepared list 

 of the names of the quadrupeds and birds; this appears in an 

 appendix to the report. Mr. Kelley also gave valued assistance 

 in the dissections. 



To better inform himself on the subject of the gait of the horse, 

 the author has observed the impressions made by the hoofs on a 

 sand -beach. In this connection he desires to express his acknowl- 

 edgments to Dr. M. H. Cryer for valuable assistance and sug- 

 gestions. 



The great delay that would be occasioned in the preparation of 

 this essay by subjecting every statement based upon observation to 

 the test of anatomical demonstration, caused the writer to remain 

 content with making many of the conclusions rest upon the evidence 

 presented by the phenomena recorded by the photographs. He is 

 aware that such conclusions are not in all respects satisfactory. 

 The several heads under which the appearances are discussed must 

 be looked upon as themes which suggest research rather than sum- 

 maries of work already done. It is hoped that the notes may 

 stimulate some of his readers to attempt to confirm the writer's 

 impressions and further to extend the application which can be 

 made of the pictures to the important subject of animal locomotion. 



The *' materials" are so arranged as to make two main groups 

 of notes, — those pertaining to the action of the limb M'hen on the 

 ground and those pertaining to the action of the limb about to 

 leave the ground and when in the air. To these will be appended 

 a short section on the human subject, on zoological considerations, 

 and on flight. Occasional repetitions of statements of facts iiave 

 been difficult to avoid in preparing the notes. The inconvenience 

 arising from this defect has been in a measure overcome by the 

 use of cross-references. 



The Use of Terms. 



It is necessary to propose the use of a few terms which will 

 clearly express in a word a meaning which otherwise would re- 

 quire the employment of a cumbersome phrase. The Avords flex- 

 ion, extension, abduction, adduction, pronation, and supination 

 imperfectly express many animal movements. Thus no adequate 

 word exists for the movement of the hand upward and downward 



