346 



NERVOUS SYSTEM OF VERTEBRATES. 



regions are given the name of the senso-motor areas. Three 

 sensory centers are recognized, the visual, the auditory and the 

 somaesthetic areas. The last is the area for general bodily sen- 

 sations. Since motor tracts descending from the visual and 

 auditory fields are not well known, a general area corresponding 

 roughly to the somaesthetic area is commonly known as the motor 

 area. The only way of describing the limits of these areas is 



Fig. 175. The primordial areas in the cerebral hemispheres, lateral surface. 

 From Flechsig (Einige Bemerkungen u.s.w.). The numerals indicate the order 

 of myelinization of the several areas. The areas 9-13, although myelinated early 

 have no projection fibers. The areas 1-8 belong to the primary sensory areas 

 (compare Figs. 179 and 180). 



by means of the superficial sulci and gyri of the brain. Their 

 position will be described here in a general way; for their exact 

 boundaries the student must be referred to the original articles 

 dealing with the subject. 



i. The somaesthetic area. This includes the central gyri, the 

 lobulus paracentralis and part of the adjacent frontal gyri and 

 of the gyrus fornicatus; that is, a part of the lateral and mesial 

 surfaces of each hemisphere in the middle region. The extent 



