Identifier: textbookofphysio1916howe (find matches)
Title: A text-book of physiology : for medical students and physicians
Year: 1916 (1910s)
Authors: Howell, William H. (William Henry), 1860-1945
Subjects: Physiology Medicine
Publisher: Philadelphia and London : W. B. Saunders Company
Contributing Library: Yale University, Cushing/Whitney Medical Library
Digitizing Sponsor: Open Knowledge Commons and Yale University, Cushing/Whitney Medical Library

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edmammalia as compared with the lower vertebrates. The infra-granular cells, on the other hand, constitute a primitive layer whichhas obvious connections, through projection fibers, with the under-lying parts of the brain and of the body at large. These cellsform, therefore, a mechanism through which the brain is connecteddirectly with the rest of the body, and through which the older 188 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. instinctive reactions are controlled. In the matter of lami-nation and distinct variations in size and appearance of thestrata of cells and fibers the human cortex shows a greater dif-ferentiation than in the lower animals, and it is especiallycharacterized by a large development of what are known asassociational areas (p. 223), particularly in the frontal lobe.In the third place, the central nervous system throughout thevertebrates is constructed upon the same lines, a mechanism ofinterconnecting neurons. There is a vast difference in the men- V Mtvi ti v< L-
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Fig. 85.—Sections through corresponding parts of the cortex in: o, Man; ?>, dog;and c, mole,, to show the greater separation of the nerve cells in the higher animals.(Bethe, after Nissl.) tal activity of a frog and a man, but the cortex of the cerebrumshows a fundamental similarity in structure in the two cases.In addition to the variations in stratification or lamination referredto above one general distinction that comparative anatomy is ableto make is that in the higher animals the greater mental develop-ment is associated with a greater complexity and richness in the con- GENERAL PHYSIOLOGY OF THE CEREBRUM. 189 nections of the neurons. As shown in Figs. 84 and 85, the number ofprocesses, particularly the dendritic processes, is much greater inthe cortical cells of the higher animals; or, to put this fact in anotherway, the number of cells in the cortex of the higher animals is muchless for an area of the same size than in lower animals. The amountof in-between substance or th

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