Anthropology Past and Present

1891 Science  
Known as the Early Journal Content, this set of works include research articles, news, letters, and other writings published in more than 200 of the oldest leading academic journals. The works date from the mid--seventeenth to the early twentieth centuries. We encourage people to read and share the Early Journal Content openly and to tell others that this resource exists. People may post this content online or redistribute in any way for non--commercial purposes. Read more about Early Journal
more » ... out Early Journal Content at http://about.jstor.org/participate--jstor/individuals/early-journal--content. JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people discover, use, and build upon a wide range of content through a powerful research and teaching platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not--for--profit organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please contact support@jstor.org. SCIENCE. SCIENCE. nevertheless, that there is a small volvula which lies, as in Lepidosteus, in the posterior part of the optic ventricle. One curious result of the development of a volvula is the peculiar course by which the fourth cranial nerve reaches its centre. Entering at the usual place in the valve, it has to traverse a large part of the volvula before making its exit from the brain. In the drum (Haplodonotus) the brain as a whole is exceedingly short. This shortening has the effect to tilt the optic lobes and cerebellum at a considerable angle with the axis of the brain, and to roll the volvula into a spherical mass with three folds, which are packed closely into the cavity of the ventricle. The main lobe of the cerebellum also has a short cephalad spur. In the cat-fish family the cerebellum, instead of projecting backward, is thrust cephalad, affording a very good and constant differential character. The few illustrations here cited are derived from a memoir about to appear in the Journal of Comparative Neurology, where a wider range of comparison and full illustration may be possible. It will be noticed that in the above cases the gray or granular material is ental. It has been shown by Professor His that the nervous elements in the spinal cord and medulla arise from the ventricular epithelium. This the writer has show is also the case in the cerebellum, at least in reptiles and fishes. In the massive cerebellum of mammals we are struck by the difficulty which stands in the way of the carrying out of the same fundamental plan of structure. The active cells are separated from the epithelium by impervious masses of fibres. How, then, do these cells reach their destination? This important question we at first sought to solve by discovering in some embryonic stage an eversion similar to that described in reptiles. This proved to be a valuable clew, but not actually correct, though a tendency to revolve from behind forward is very pronounced in the cerebellum of birds, and is exhibited in the direction of the lobules of the cerebellum in marsupials. But, while there is not an actual eversion of the cerebellum in mammals, there is a time when a pouch from the lateral posterior walls of the fourth ventricle is formed. This divertacle envelops the cerebellum and meets its fellow of the opposite side. In a short time this sac flattens out, and both layers fuse with the ectal surface of the cerebellum, and constitute a temporary proliferating organ from which the cells are derived. These cells migrate to a point beneath the layer of Purkinje's cells, the origin of which seems to be also from the ventricular epithelium. Although this process has been observed only in rodentia there can be no doubt that it prevails in other groups of mammals. Although somewhat unexpected, this method is not unlike that which Professor His has described for the origin of the olives and related structures of the medulla. By this provision the increase of ectal surface through the convolutions of the cerebellum provides for the largest possible enlargement of the active centres with the most economical distribution of fibres. This discovery may serve to enforce the value of a comparative method in approaching a complicated problem like t.he present one. C. L. HERRICK. JOHN GILMER SPEED follows up his article in the September Lippincott's with a paper entitled " The Common Roads of Europe." He shows how far ahead of us the great nations of Europe
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