6 BIOLOGY AND SOCIAL PROBLEMS 



tains other elongated organs than nerves, as, 

 for example, muscles and, particularly, blood 

 vessels, the cells of these parts are in no wise 

 elongated as the cells of the nervous system 

 are. In this respect the nervous system seems 

 to be unique. 



Described from the standpoint of the histo- 

 logical elements composing it, the nervous 

 system of man and the other higher animals 

 may be said to be made up of an enormously 

 intricate system of interwoven neurones. The 

 number of these elements in such a nervous 

 system is incredibly great and certainly reaches 

 many, many millions. The complexity of their 

 arrangement is familiar to every reader of 

 textbooks on neurology, but even the most 

 involved descriptions in the texts are as sim- 

 plicity itself compared with the real complex- 

 ity in such a nervous system as that of any of 

 the higher animals, not to mention man. 



Yet, notwithstanding the enormous com- 

 plexity in the arrangement of the neurones in 

 such animals, these elements are capable of a 

 relatively simple classification. A large num- 

 ber of them extend from the skin and the or- 

 gans of special sense, such as the nose, the 

 tongue, the ear, and the like, to the central 



