NERVOUS SYSTEM 



This very complicated system may be studied in its 

 gross structure for the coarser points, but to understand 

 anything of the finer structure, histological methods must 

 be applied. The morphological unit of the system con- 

 sists of a modified cell called the neurone. It is a special- 

 ized cell consisting of a cell body with connecting fibers 

 that connect or rather associate it with other neurones of 

 the rest of the system. Nerve cells should be studied in 

 prepared slides so that their structure may be understood. 

 The whole system consists of a multiplication of these units 

 in their many forms. They are the units of structure 

 but not the physiological units of the system. The physio- 

 logical unit consists of two or more, of these cells consist- 

 ing of an effector, receptor and an adjust or. These make 

 up a simple reflex unit and are the basis of the whole 

 system. 



The development of this system has been a long one 

 historically and to understand it thoroughly, it must be 

 approached from both the embryological and histologi- 

 cal sides. The development of the parts must be taken up 

 with the reason for the development. Each sense has 

 associated with it, centers in the system that are devoted 

 to that one sense. To keep the machine harmonious, there 

 must be interconnections, so that in a brain as simple as 

 that of Necturus, the complication has already reached 

 formidable proportions. 



The nervous system is easily prepared for study in 

 Necturus and all of the work taken up in this section can 



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