The American journal of the medical sciences . Fig. VIII. Fig. YII. represents one of these communications between the two sides,seen in the skin of the abdomen of the frog, following, as is very fre-quently the case, one of the small bloodvessels, a ; h, the trunk of a nerve;c and d, nerve-angles of three bundles of fibres. Fig. YIII., a, nervous plexus from the under side of the head of askate, Raia hatis; a and h, twonerves, one on the right and the otheron the left of the median line ; c, anerve-angle of two bundles of fibres;d, a nerve-angle with three the two trunks, a an
The American journal of the medical sciences . Fig. VIII. Fig. YII. represents one of these communications between the two sides,seen in the skin of the abdomen of the frog, following, as is very fre-quently the case, one of the small bloodvessels, a ; h, the trunk of a nerve;c and d, nerve-angles of three bundles of fibres. Fig. YIII., a, nervous plexus from the under side of the head of askate, Raia hatis; a and h, twonerves, one on the right and the otheron the left of the median line ; c, anerve-angle of two bundles of fibres;d, a nerve-angle with three the two trunks, a and h, arevarious c0mmunicating branches. Theinterchange of fibres in this specimenis greater than is commonly the case,especially at the lower part of thefigure. Nevertheless we have suc-ceeded in tracing, without difficulty,communications of different degreesof complexity, between the right and. 1864.] Wyman, Passage of Nerves across Middle Line of Body. 851 left halves of the nervous system, at almost every point on the roof of themouth and in the skin of the abdomen in frogs, and in various parts of theinteguments of the under side of the body in skates. Physiological questions of considerable importance grow out of the ana-tomical conditions described above. The experiments of Drs. Mitchell andMorehouse prove that certain motor fibres actually do cross the median lineand influence muscles on the side opposite to that of the half of the cen-tral axis from which they arise. The extent of their influence, it is true, isconfined within very narrow limits. Have the sensitive nerves an analo-gous relation to the two sides of the body ? May an impression madeupon a given point on the skin be carried to the chord across the medianline ? We are aware of no experiments which give an answer to thesequestions. The answer from pathology as far as it goes is in the Copeland
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