ZOOGENY. ID.") 



. Organ is distinguished from system in not pur- 

 suing its course through the whole body, nor consisting 

 simply of one and the same mass, but by its occupying 

 a definite part of the body and being composed of several 

 systems. 



2367. Every organ has therefore a special and specific 

 function also. 



2368. The systems of animal life divide only into two 

 kinds of organs, into those of sensation and those of 

 motion, into the solar and planetary, or central and 

 peripheric. 



a. MOTOR ORGANS. 



2369. Bone and muscle are not societies, but only 

 poles of one system. There is therefore no mere bony 

 organ, and no mere muscular organ. Meanwhile we will 

 here regard them in particular or " per se." 



1. Osseous Organs. 



2370. The first bones were branchial arches or tra- 

 cheal rings. When the lungs were developed from the 

 branchiae, the branchial arches were repeated as ribs or 

 pulmonary arches. Lastly, should bones be formed, which 

 are to be wholly in the service of the animal or the nerv- 

 ous system, so also must they be wholly liberated from 

 the vegetative organs, and become self-substantial, i. e. 

 have nothing else to do, but move. Free motor organs 

 can be none other than ribs that have become free. 



2371. These free ribs must inclose the respiratory 

 organ, which has become an organ of animal life or the 

 integument; they are the members or limbs. If we 

 think of ribs, whose office is no longer to inclose lungs, 

 which must no longer be subservient to the uninterrupted 

 vital motion of respiration, and which are no longer united 

 by pleura into a closed bladder or sac will not such 

 simply retain the self-substantial voluntary motion in 

 themselves ? will they net abandon the inferior cystic 

 form, and represent the same, though but ideally and 

 voluntarily ? will not such a thorax open in front, like the 



