. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE SPINAL CORD—GENERAL. 481 stance. The cord may be regarded either as an instrament for the reception and generation of impulses independent of the. J^G. 343.—Transverse section of spinal cord of child six months old, at middle of lumbar region, showing especially the flbers of gray substance. 1 x 80. (After Gerlach.) a, ante- rior columns; 6, posterior columns; c, lateral columns; d, anterior roots; e, posterior roots; /, anterior white commissu
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. THE SPINAL CORD—GENERAL. 481 stance. The cord may be regarded either as an instrament for the reception and generation of impulses independent of the. J^G. 343.—Transverse section of spinal cord of child six months old, at middle of lumbar region, showing especially the flbers of gray substance. 1 x 80. (After Gerlach.) a, ante- rior columns; 6, posterior columns; c, lateral columns; d, anterior roots; e, posterior roots; /, anterior white commissure; ff, central canal lined by epithelial cells; A, con- nective-tissue substance surrounding it; i, transverse flbers of gray commissure in front, and fc, the same behind central canal; Z, two veins cut across; m, anterior cornua; n, great lateral cell group of anterior cornua ; o, lesser anterior cell group (column); js, smallest median cell group; q, posterior cornua; r, ascending fasciculi in posterior cornua; s, substantia gelatinosa. brain; or as a conductor of afferent and efferent impulses des- tined for the brain or originating in that organ. As a matter of fact, however, it is better to bear in mind that the cord and brain constitute one organ or chain of organs, which, as we have learned from our studies in development, are differentia- tions of one common track, originating from the epiblast. While the brain and the cord may act independently to a very large extent, as may be shown by experiment, yet it can not be too well borne in mind that in the actual normal life of an animal such purely independent behavior must be exceed- ingly rare. We are constantly in danger, in studying a sub- ject, of making in our minds isolations which do not exist in nature. When one accidentally sits upon a sharp object, he 81. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of t
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