FUNCTIONS OF THE SENSORY GANGLIA. 657 



consciousness. If it be laid upon the back, it rises again ; if pushed, it 

 walks. If a Bird thus mutilated be thrown into the air, it flies ; if a Frog 

 be touched, it leaps. It swallows food and liquid, when they are placed in 

 its mouth ; and the digestive operations, the acts of excretion, etc., take 

 place as usual. In the case of a Pigeon experimented on by Malacorps, 

 which is recorded by Magendie, there appears sufficient proof of the per- 

 sistence of a certain amount of sensation. Although the animal was not 

 affected by a strong light suddenly made to fall upon l;s eyes, it was accus- 

 tomed, when confined in a darkened or partially-illuminated room, to seek 

 out the light parts; and it avoided objects that lay in its way. In the same 

 manner, it did not seem to be affected by sudden noises; but at night, when 

 it slept with its eyes closed and its head under its wing, it would raise its 

 head in a remarkable manner, and open its eyes, on the slightest noise ; 

 speedily relapsing into a state of complete unconsciousness. Its principal 

 occupation was to preen its feathers and scratch itself. And Longet men- 

 tions that a Pigeon from which he had removed the entire Cerebrum, gave 

 many indications of consciousness of light; for not only did the pupil con- 

 tract, but the lids closed, when a strong light was suddenly made to fall 

 upon the eye, the animal having been previously kept in darkness ; and 

 ivlien a lighted candle was made to move in a circle before it, the animal ex- 

 ecuted a corresponding movement with its head. 1 The condition of such 

 beings seems to resemble that of a Man, who is in a slumber sufficiently 

 deep to lose all distinct perception of external objects, but who is yet con- 

 scious of sensations, as appears from the movements occasioned by lights or 

 by sounds, or from those which he executes to withdraw the body from an 

 uneasy position. 



525. The results of other experiments made upon the Sensory ganglia 

 themselves, and upon the organs from which they derive their impressions, 

 confirm this view; by showing that the ordinary movements are seriously 

 perturbed, and that in some instances a new set of automatic movements is 

 induced, when the normal relations between the sensory and motor appa- 

 ratus are disarranged, Of the functions of the ganglia of special sense, those 

 of the Corpora Qnadrigemina are the chief which have been examined ex- 

 perimentally. The researches of Flourens and Hertwig have shown, that 

 the connection of these bodies with the visual function, which might be in- 

 ferred from their anatomical relations, is thus substantiated. The partial 

 loss of the ganglion on one side produces partial loss of power and temporary 

 blindness on the opposite side of the body, without necessarily destroying 

 the mobility of the pupil ; but the removal of the larger portion, or complete 

 extirpation of it, occasions permanent blindness and immobility of the pupil, 

 with temporary muscular weakness on the opposite side. This temporary 

 disorder of the muscular system sometimes manifests itself in a tendency to 

 move on the axis, as if the animal were giddy. No disturbance of conscious- 

 ness appears to be produced ; and Hertwig states that he never witnessed 

 the convulsions, which Flourens mentions as a consequence of the operation, 

 and which were probably occasioned by his incision having been carried too 

 deeply. As Louget has justly remarked, it is difficult, if not impossible, to 

 remove one or both of these gaugliouic masses, without doing such an injury 

 to the Crura Cerebri on which they repose, as shall in great degree account 

 for such disturbed movements ( 529). Irritation of one of the Tubercula 



1 It must not be forgotten that, in such experiments, the severity of the operation 

 will of itself occasion a suspension or disturbance of the functions of parts that re- 

 main ; so that the loss of a power must not be at once inferred from the absence of 

 its manifestations. But the persistence of a power, after the removal of a particular 

 organ, is a clear proof that it cannot be the peculiar. attribute of that organ. 



