File:An American text-book of physiology (1897) (14783295205).jpg

Identifier: americantextbook00howe (find matches)
Title: An American text-book of physiology
Year: 1897 (1890s)
Authors: Howell, William H. (William Henry), 1860-1945 Bowditch, H. P. (Henry Pickering), 1840-1911
Subjects: Physiology
Publisher: Philadelphia : Saunders
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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* Arch. fUr die gesammle Physiologic, Bde. 33 u. 34, 1884.45 70G AN AMERICAN TEXT-HOOK OF PIIYSIOLOC Y. liemispherts (inclii(liii«; the coi-jjora striata as well as the iiiajitlc) be removed,the animal apparently suffers little ineonveniencc. The movements are undis-turbed ; sueh fish play together in the usual manner, discriminate between aworm and a bit of stiing, and among a series of colored wafers to which theyrise, always select the red ones first. In these fish the eye is the controllingsense-organ, and, as will be recognized (see Fig, 199), the operation has by nomeans damaged the primary centres of vision. Quite different is the result when the cerebrum is removed from a shark.^Tn this case, although the eyes are intact, the animal is reduced to comj)letequiescence; yet on the whole, the nervous system of the shark is rather lesswell organized and more simple than that of the bony fish. The astonishingeffect produced is explained by a second experiment (see Fig. 200). If the
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Fig. JOO.—Schema of the cncephalon of a cartilaginous fish (Edinger). The vertical lilack line marksoif the striatum and pars olfactorius, which lie in front of the thalamus. olfactory tract be severed on one side, no marked disturbance in the reactionsof the shark is to be noticed; when, however, both tracts are severed, theshark acts as though deprived of its cerebrum. From this it appears thatthe removal of the principal sense-organ, that of smell, is the real key to thereactions, and that the responsiveness of the fish is reduced in the first instance,becau.se in this case it has been deprived of the impulses coming through theprincipal organs of sense, and in the second the removal of the cerebrum ismainly important because the cerebrum contains the pathway for the impulsesfrom the olfactory bulbs to the cell-groups which control the cord. Passing next to the amphibia as represented by the frog, there are sevemlseries of observations on the physiological value of the divisions

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