File:A text-book of human physiology (1906) (14583890379).jpg

Identifier: textbookofhumanp00tige (find matches)
Title: A text-book of human physiology
Year: 1906 (1900s)
Authors: Tigerstedt, Robert, 1853-1923 Murlin, John R. (John Raymond), b. 1874, tr
Subjects: Physiology
Publisher: New York and London, D. Appleton and Co.
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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al lobe. ^ For the sake of simplicity, the different fields in this figure have been represented asif they were sharply distinct from one another, whereas in reality tiiere are no sharpboundaries demonstrable, either between the smaller areas or the larger areas. One fieldalways passes gradually into the other. THE MOTOR AREAS 637 outang, and those of Sherrington and Greenl)auni on the orang-outang, gorillaand the chimpanzee, are of very great interest partly hecause these anthropoidapes stand closest in the scale to man himself, and partly for the specialreason that a further progressive development of this zone from the monkeysto the highest apes is therein unmistakably demonstrated. The fact of thisdevelopment teaches us in the clearest possible manner how careful we mustbe in applying the results obtained from other animals to man himself. The general division of the motor zone as it has been made out in themonkeys is the same in its larger features for the apes. There are however
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55 >» a ^ J Arrangement of excitable fibtrs in the internal capsule.Fig. 287.—Motor cortical areas in the monkey (.Macacus xinicus), after Bcevor and IIorslej\ several very iiolcworthy (litlcicnccs hctwccii the two groups. In the monkeys(cf. Fig. 285) we liiul on the convex surfaces. l)olh on the central and thefrontal convolutions, single excitable regions from which several kinds ofinoveincnts can be discharged. In the apes (cf. Fig. 288) the region on thefrontal convolutions contains but one field from which only movements ofthe eyes can be induced. The posterior central convolution is entirely or inverv huge part inexcitable. the motor cortical areas being for the most partgathered together in the anterior central convolution. Again, wliereas in themonkeys there are no sliarp demarcations between the cortical areas fordifferent groups of muscles, in the orang-outang the cortical areas for themain divisions of the body are separated by regions which are inexcitable. 638 PHYSI

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