. An elementary course of practical zoology. Zoology. 156 THE FROG bridge is traversed from end to end by a very narrow longi- tudinal canal, the central canal {), so that the cord is not a solid cyUnder, but a tube with an extremely narrow cavity and excessively thick walls. The section also shows that the cord is not homogeneous, but is composed of two different substances. Its outer part is pure white and shining in the fresh cord, and is hence ziA. Fig. 48.â section of spinal cord of frog. c. c. central canal; dorsal fissure ; d. h. dorsal horn of grey matter â d. r. fib
. An elementary course of practical zoology. Zoology. 156 THE FROG bridge is traversed from end to end by a very narrow longi- tudinal canal, the central canal {), so that the cord is not a solid cyUnder, but a tube with an extremely narrow cavity and excessively thick walls. The section also shows that the cord is not homogeneous, but is composed of two different substances. Its outer part is pure white and shining in the fresh cord, and is hence ziA. Fig. 48.â section of spinal cord of frog. c. c. central canal; dorsal fissure ; d. h. dorsal horn of grey matter â d. r. fibres of dorsal root of spinal nerve ; nv. c. nerve cells of dorsal horn ; nv. c'. nerve cells of ventral horn ; p. w. pia mater ; ventral fissure ; v. h. ventral horn of grey matter ; v. r, fibres of ventral root of spinal nerve ; w. ?«. white matter. (After Howes.) called the white matter {). Its internal substance has a pinkish colour when fresh, and is called the grey matter {, ). The grey matter has a squarish outline in trans- verse section. It surrounds the central canal, and is con- tinued upwards and downwards, forming what are called the dorsal {) and ventral () horns of the grey matter. The Brain.âIn front the spinal cord passes insensibly into the brain (Fig. 49), which is of somewhat greater diameter than the cord, and is made up of several very dis-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Parker, William Newton, joint author. London, Macmillan and Co. , Limited; New York, The Macmillan Company
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