30 



ANIMAL LOCOMOTION. 



with in all ; and this appears to me an all-sufficient reason 

 for attaching great importance to the movements of soft 

 parts, such as protoplasm, jelly masses, involuntary and volun- 

 tary muscles, etc.^ As the muscles of vertebrates are accu- 

 rately applied to each other, and to the bones, while the bones 

 are rigid, unyielding, and incapable of motion, it follows that 

 the osseous system acts as a break or boundary to the muscular 

 one, — and hence the arbitrary division of muscles into exten- 

 sors and flexors, pronators and supinators, abductors and ad- 

 ductors. This division although convenient is calculated to 

 mislead. The most highly organized animal is strictly speaking 

 to be regarded as a living mass whose parts (hard, soft, and 



Fig 9.— The Superficial Muscles in the Horse, (after Bagg). 



otherwise) are accurately adapted to each other, every part 

 reciprocating with scrupulous exactitude, and rendering it 

 difficult to determine where motion begins and where it ter- 

 minates. Fig. 9 shows the more superficial of the muscular 

 masses which move the bones or osseous levers of the horse, 

 as seen in the walk, trot, gallop, etc. A careful examination 

 of these carneous masses or muscles will show that they run 



^ Lectures " On the Physiology of the Circulation in Plants, in the Lower 

 Animals, and in Man," by the Author.— Edinburgh Medical Journal for Sep- 

 tember 1872. 



