SPECIAL PHYSIOLOGY. 49 



portion, we find masses of globules serving as reflecting cen- 

 tres, transforming the sensory impressions into motor effects ; 

 moreover these centres are better defined and their irradia- 

 tions more localized than those in the proper spinal cord. 



In the cephalic region there are found a series of centres 

 beginning low down and going upwards (or from behind for- 

 wards), for whose exact determination modern physiological 

 investigations are especially applied ; we shall only now cito 

 the example of a few of the most important, as these centres 

 will be more exactly pointed out, as well as their centripetal 

 and centrifugal nerves, when the different functions over which 

 they preside are considered. 



In the bulb is found : the centre of deglutition ; of the 

 movements of mastication ; expression of imitation ; of 

 speech (olivary bodies, according to Schroeder van der Kolk, 

 and Duchenne, of Boulogne: consequently, in this centre 

 should the cause of those singular paralyses, known by the 

 name of labio-glosso-pharyngeal, be sought) ; the centre of 

 respiratory movements : this centre is composed of a little 

 mass of gray substance situated towards the point of the cala- 

 mus scriptorius (floor of the fourth ventricle), this is the 

 point or vital knot (Flourens, Longet), so-called because its 

 lesion causes in cold-blooded animals an instantaneous death, 

 and this simply by an immediate arrest of respiration (see 

 respiration, influence of oxygen and carbonic acid upon 

 the respiratory centre) ; the centre of cardiac movements 

 (moderating fibres of the pneumo gastric) ; a portion of the 

 vaso-motor centres (Ludwig, Thiry). 



At the protuberance, and as high up as the cerebral pedun- 

 eules, are found : another portion of the vaso-motor centres 

 (Tcheschichin) ; the centres ofinnervation of the movements 

 of locomotion : these last-named centres appear to be in com- 

 munication with the different encephalic centres, properly so 

 called, which are attached to the protuberance by peduncles 

 (middle cerebellar peduncles and cerebral peduncles). Le- 

 sions of these peduncles occasion a disturbance in the co- 

 ordination of movements ; unilateral lesions give rise to the 

 peculiar movements of rotation, which occur under the form 

 of whirling (a continuous motion around some imaginary 

 central point), or of motion on a pivot (the posterior portion 

 of the animal remains fixed whilst the anterior portion re- 

 volves around the former as a centre), or of a rolling motion 

 (rotation around the longitudinal axis of the body), or of 

 somersaults (sudden movements forwards or backwards). 



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