36 LABORATORY OUTLINE OF NEUROLOGY 



and V cranial nerves this is the visceral motor column and is 

 the forward extension of the lateral gray column of the spinal 

 cord; (3) a longitudinal ridge with a beaded contour, which 

 contains the terminal centers of the visceral sensory com- 

 ponents of the X, IX, and VII cranial nerves the vi ceral 

 sensory column; (4) separated from the last by a deep groove 

 and forming the dorso-lateral wall of the fourth ventricle is 

 the somatic sensory column. This column is the continuation 

 of the dorsal gray column of the spinal cord, and its ventral 

 part contains the centers for the general cutaneous nerves of 

 the trunk and head. The dorsal part of this column is the 

 area acustico-lateralis, whose anterior end is greatly enlarged 

 under the cerebellum, with which it is directly continuous. 

 This area receives the VIII and lateral line nerves, and the 

 cerebellum is a specialized derivative of it. The longitudinal 

 groove between columns 2 and 3 is the sulcus limitans (cf . the 

 development of the human brain, Section 38). It separates 

 motor centers below (ventrally) from sensory centers lying 

 farther dorsally. 



24. From these observations it appears that the brain 

 shows various external thickenings or enlargements, each of 

 which is related to a particular physiological type of end- 

 organ. We may, in fact, recognize a "nose brain," "eye 

 brain/' "ear brain," etc., and in addition the cerebellum 

 above these primary sensorimotor centers. There is no 

 cerebral cortex. 



25. Draw the medulla oblongata from the dorsal side, twice 

 natural size, after removal of the membranous roof , to illustrate 

 the functional areas in the walls of the fourth ventricle. In 

 this drawing the functional columns should be tinted to cor- 

 respond with the colors used in the drawing of the peripheral 

 nerves (Section 21). Thus, the acoustico-lateral area will be 

 colored the same as the VIII and lateral line nerves, the gen- 

 eral somatic sensory area the same as the general cutaneous 

 nerves, etc. The drawing of the entire brain called for in 

 Section 21 may also be tinted in the same way. 



26. The physiologically distinct areas noted in the preceding 

 sections tend to be grouped in larger regions, the pattern of this 

 grouping being determined in part by the primitive segmenta- 



