256 LIFE, IN ITS HIGHER FORMS. 



In like manner every lateral nerve is double, arising by 

 two distinct roots, the one from the motor, the other from 

 the sensitive tract. 



Besides these, there are series of nerves, extensively 

 ramified, which do not originate from either brain or spinal 

 column, but from scattered ganglia situated in various parts 

 of the body, and destined to supply those important organs 

 whose motions are independent of the will, and which 

 are therefore distinguished as the organic or vegetative 

 system. 



The blood is, in every case, composed of red " globules" 

 or (more properly) disks, suspended in a watery fluid. 

 It circulates through two series of vessels, which ramify 

 to every part of the body. The one series — that of the 

 veins — receives the assimilated nutriment from the diges- 

 tive system, and conveys the blood, so reinforced, but 

 exhausted of its oxygen, to the heart, a great muscular 

 chamber, which alternately contracts and expands without 

 intermission. By these movements, the contained volume 

 of blood is urged forward, in whole or in part, to the 

 lungs, or (in such animals as are aquatic) to the gills, 

 where it is brought into proximity with fresh oxygen, 

 either from the inhaled air or water. This element 

 readily combines with the blood through the excessively 

 attenuated coats of the vessels, and revivifies it, restoring 

 at once its brilliant red hue. Thus renewed, the vital 

 fluid is returned to the heart, whence it is forced into 

 the other series of vessels called arteries, which carry it 

 forward to all parts of the body, and at length, uniting 

 with the veins by excessively minute tubes called capilla- 

 ries, situated at the circumference, and having built up 



