360 BIOLOGY. 



for themselves, a sense of touch, such as the blossom 

 might have in the instant of the pollenization. 



2033. As all formations have become symmetrical 

 through and in accordance with the vascular system, so 

 does the vegetative nervous system separate into two 

 parallel stems which accompany the arterial trunk. They 

 are called intercostal nerves. These ramify and form 

 plexuses that accord with the visceral organs, which they 

 govern. 



b. Animal Nervous System. 



2034. The animal nervous system is the repetition of 

 the vegetative, and is combined therewith to constitute 

 an unity. The nervous cyst that was previously dis- 

 severed in a reticular manner, becomes a closed tube, 

 which is placed upon the light-exposed side of the other 

 animal systems, and thus upon the vertebral column. 

 This closed nervous tube is called the myelon, or spinal 

 cord. 



2035. The spinal cord is worth as much as all the 

 visceral nerves taken together ; it is the felted system of 

 intercostal nerves ; and is, properly speaking, none other 

 than the posterior double cord of ganglia. It consists 

 therefore also of ganglia and plexuses, but both have 



\ coalesced, on account of the increase of the mass and its 



endeavour towards the attainment of union. 



2036. The ganglia form a tube, which is inclosed by 

 the tubes of the plexuses. The ganglion-tube is the 

 gray, the plexus-tube the medullary substance. 



2037. If the gray substance appear to reside within 

 the medulla, this is the result only of involution or a 

 folding in. The parietes of the spinal marrow stand 

 therefore in everlasting tension with each other, like 



q w ganglia and plexuses, and like arteries and veins. 



2038. The spinal marrow is the content of the bones 

 M and muscles, like the intercostal nerves or the visceral 



cord are the contents of the abdominal cavity, and as the 

 blood is that of the internal and fibrous coat of the 

 arteries. Bones and muscles are the animal parietes of 



