io6 Animal Morphology. 



arch, and has its own tripartite membrane serous, muscular, 

 and mucous. 



The ribs, sternum, and cartilages represent the mucous 

 membrane, the intercostal muscles, and the diaphragm, with 

 the abdominal and perineal muscles changed and modified, 

 with the abdominal ribs arrested in development, so as to 

 allow freer motion of the trunk upon the limbs ; these all 

 combined represent the muscular or contractile membrane; 

 and the synovial sacs placed at the ends of the ribs represent 

 the serous membrane. Segmentation in the serous mem- 

 brane at the heads of ribs is here represented in a very com- 

 plete form ; with the attempt in the sternum, in man and 

 most mammalia, to form one continuous portion of bony 

 membrane, alias mucous membrane. 



Again, as contrasted with the interosseous muscles, the 

 various directions and forms of distribution of the abdominal 

 muscles must be viewed as a species of muscular segmentation. 



So that one of the first indications of this sense apparatus 

 is segmentation, which must be viewed as a kind of diffe- 

 rentiation in the main, distinct from that of the differentiation 

 in organic life ; arising from the fact that membrane repeats 

 itself in the form of continual segmentation in all its tripartite 

 divisions. Again, in the great change in differentiation 

 of the several divisions, the contractile membrane and the 

 mucous membrane one as the striped muscle of animal life, 

 the other as bone and cartilage, and the third very little 

 removed in cell differentiation, as synovial membrane, from 

 serous membrane in the vegetative organs of the body 

 the principle of segmentation, which appears to be abhorred 

 in the one, is common in the other, and this makes the 

 great difference between them. 



The apparatus for protecting and defending the haemal 

 sense, as in a castle, from external injury, especially in its 

 distribution over organs which bear external pressure badly 



