The psychic development of young animals and its physical (somatic) correlation with specific reference to the brain / by Wesley Mills.

  • T. Wesley Mills
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: The psychic development of young animals and its physical (somatic) correlation with specific reference to the brain / by Wesley Mills. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    not sj»ontaiieous, are nearly as perfect afterwards as before, and much liht is tlirown on the nature of reflexes, I liave, after careful investigation, been unable to tiud any motor •cortical centres whatever. The whole cerebral cortex appears to be ah.solutely inexcitable. except, [)erliaps, as concerns certain eye move- ments. and as for these a strong stimulus is required, it is doubtful if they are of cortical origin in the usual sense of the term. Nevertheless, unless we deny the existence of voluntary movements to the bird—an extreme position—we are landed in physiological diffi- culties, inasmuch as it has been a.ssumed b}' nearly all ]ihysiologists that th(‘ cortex is essential to voluntary movements. The case of the bird seems to me to show that we have much to learn as to the nervous mechanism of voluntary movements, notwithstanding all the investiga- tion that has been given to this subject. CONCLUSIO.VS. In the dog and the cat there is a ]»eriod extending from birth to about the time of the opening of the eyes characterized by reflex move- ments, the sway of instincts and the absence of intelligence. Jturing this time the cerebral cortex is ine.xcitable by electrical stimulation, so that the psychic condition during the blind ])ei‘iod is correlated with an undevelojied state of the motor centres of the cortex of the cerebrum. The advance in movements, tirst of the limbs and later of the head and face parts, together with the ])sychic progress associated with this is correlated with the ra])id development of the cortical centres for the limbs in the first instance, and later for the head and face in the ])eriod immediately following the blind stage. This is more rapid and more pronounced in the cal than in the dog. and is correlated with the greatei- control in the cat over the fore-limbs and with certain physiological and ])sychic developments chai’acteristic of the cut. Similar conclu.sions apply to the rabbit, except that the difference in the rapidity of development of head and face movements is correlated with an earlier organization of the corresponding cortical centres, and that thei’C is a greater ditierence between the fore-limb and the hind- limb, with all of which there are special psychic conrlations bound up with certain peculiarities of the rabbit’s modes of life. The vast difference in physiological and psychic development of the cavy at birth is correlated with the presence of cortical cerebral centres readily excited by artificial stimuli, centres which in a few days reach a practically perfect stale of develojjment. The psychic manifestations of the ])igeon and the fowl have not the same sort of cerebral cortical correlates as the animals refen-ed to above.
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