ANIMAL LOCOMOTION. 



superior and inferior extremities, and more especially of the 

 trunk, are arranged in longitudinal, transverse, and oblique 

 spiral lines, and in layers or strata precisely as in the 

 ventricles of the heart and hollow muscles generally.^ If, 

 consequently, I eliminaLe the element of bone from these 

 several regions, I reproduce a typical hollow muscle; and 

 what is still more remarkable, if I compare the bones re- 

 moved (say the bones of the anterior extremity of a quad- 

 ruped or bird) with the cast obtained from the cavity of a 

 hollow muscle (say the left ventricle of the heart of the 

 mammal), I find that the bones and the cast are twisted 

 upon themselves, and form elegant screws, the threads or 

 ridges of which run in the same direction. This affords a 

 proof that the involuntary hollow muscles supply the type or 



Fig. 6. — Wing of bird. Shows how the bones of the arm (a), forearm (?>), and 

 hand (c), are twisted, and form a conical screw. Compare with Figs. 7 

 and 8. — Original. 



Fig. 7.— Anterior extremity of elephant. Shows how the hones of the arm (g), 

 forearm (q'x), and foot (o). are twisted to form an osseous screw. Compare 

 with Figs, 6 and S.—Origi^ial. 



Fig. 8.— Cast or mould of the interior of the left ventricle of the heart of a 

 deer. Shows that the left ventricular cavity is conical and spiral m its 

 nature, a Portion of right ventricular cavity ; h, base of left ventricular 

 cavity ; x, y, spiral grooves occupied by the spiral musculi papillares ; j q, 

 spiral ridges projecting between the musculi jpapillares. Compare with Figs. 

 6 and 7. — Original. 



pattern on which the voluntary muscles are formed. Fig. 6 re- 

 presents the bones of the wing of the bird ; fig. 7 the bones of the 



1 " On the Arrangement of the Muscular Fibres in the Ventricles of the 

 Vertebrate Heart, with Physiological Remarks," by the Author.— Philo- 

 sophical Transactions, 1864. 



e 



