FUNCTIONAL DIVISIONS OF THE NERVOUS SYSTEM. 103 



motor components in ventral roots supplying musculature derived 



from the somites. 

 D Visceral motor division. Consists of: 



1. Motor nuclei in lateral horn or intermediate zone of the cord and 



corresponding region of the medulla oblongata, 

 motor component in dorsal and ventral roots supplying muscula- 

 ture derived from lateral mesoderm. 



2. Sympathetic system, efferent portion. Consists of ganglion cells 



and fibers concerned with glandular secretion, and the con- 

 tractions of smooth muscle. They receive impulses from 

 visceral efferent fibers. 



To illustrate the positions of the four divisions in the brain of 

 vertebrates two diagrams are given, Figures 46 and 47. These 

 show by conventional symbols the areas occupied by the functional 

 divisions in the brain of a fish and of man. In these figures as 

 in others the shading by right lines, either vertical or horizontal, 

 indicates somatic sensory areas; the oblique lines indicate visceral 

 sensory areas. The figures should be compared with Figs. 2, 

 3, n, and with figures of the human brain in a text-book of 

 anatomy. 



DEMONSTRATION OR LABORATORY WORK. 



1. Dissect the cranial nerves of a fish, a frog and a mammal with 

 especial reference to the cutaneous and visceral rami. 



2. Dissect the brain of a large dogfish or skate and of a large 

 Ameiurus, or other bony fish which has large vagal or facial lobes. 

 Examine the form relations of the functional divisions in the medulla 

 oblongata, and of the cerebellum, tectum mesencephali, inferior lobes 

 and olfactory lobes and bulbs by means of hemisections and dissections 

 of the brain and by sections under low power of the microscope. 



3. Compare the brain of some mammal with those of the fishes 

 with regard to each of these points. 



The importance of dissections of the brain cannot be over-estimated. 

 Very satisfactory results in demonstrations can be obtained by no more 

 elaborate means than dissections and well prepared sections stained by 

 Delafield's haematoxylin. 



LITERATURE. 



Allis, E. P., jr.: The Anatomy and Development of the Lateral Line 

 System in Amia calva. Jour. Morph., Vol. 2. 1889. 



Cole, F. J.: On the Cranial Nerves of Chimaera monstrosa Linn., etc. 

 Trans. Roy. Soc. Edinb., Vol. 38. 1896. 



