GANGLION OF THE TUBER ANNULARE. 733 



in its interior a large admixture of gray matter. It presents both transverse and longi- 

 tudinal white fibres. Its transverse fibres connect the two halves of the cerebellum. Its 

 longitudinal fibres are connected below, with the anterior pyramidal bodies and the oli- 

 vary bodies of the medulla oblongata, the lateral columns of the cord, and a certain por- 

 tion of the posterior columns. Above, the fibres are connected with the crura cerebri 

 and pass to the brain. The superficial transverse fibres are wanting in animals in which 

 the cerebellum has no lateral lobes. 



The general properties of the tuber annulare have been demonstrated in the most sat- 

 isfactory manner by Longet. In his experiments, direct excitation of the superficial 

 transverse fibres did not produce well-marked convulsive movements, and there were no 

 convulsions when the posterior fibres were stimulated. When galvanization was applied 

 to the deeper anterior fibres, convulsive movements were distinct at each excitation. 

 Stimulation of the posterior portion always produced pain. This was not constantly 

 observed to follow irritation of the anterior portion, and, when pain occurred, it was 

 thought to be due to irritation of the root of the fifth nerve. 



The above experiments, it is true, are not so free from uncertainty as those made upon 

 the more accessible parts of the encephalon, but, as far as they go, they tend to show that 

 the tuber annulare is both insensible and inexcitable in its superficial anterior portion, 

 which is composed chiefly of commissural fibres from the cerebellum ; that it is excita- 

 ble and probably insensible in its deeper anterior portion, which seems to be composed 

 chiefly of descending motor conductors ; and, finally, that it is sensible and probably 

 inexcitable in its posterior portion. 



The tuber annulare undoubtedly acts as a conductor of sensory impressions and motor 

 stimulus to and from the cerebrum, as we should naturally expect from the direction of 

 its fibres, and as has been repeatedly shown by cases of disease, particularly as regards 

 motion. In addition, however, judging from the fact that it contains numerous nodules 

 of gray matter between fasciculi of white fibres, and that this gray matter contains cel- 

 lular elements similar to those found in other nerve-centres and from which nerve- 

 fibres undoubtedly originate, it would be inferred that these nodules have a distinct 

 function and give to the tuber annulare the properties of a nerve-centre. It will be 

 interesting, therefore, to follow out the experiments upon this part, by which its action 

 as a centre has been illustrated. These experiments are of two kinds : First, the re- 

 moval of other encephalic ganglia, leaving only the tuber annulare, the medulla oblon- 

 gata, and the cerebellum, and noting the properties or faculties retained by animals 

 under these conditions. Experiments of this kind are tolerably definite, as we already 

 know the general functions of most of the other encephalic ganglia. Second, to note 

 the effects of extirpation of the tuber annulare alone. 



If the cerebral hemispheres, the olfactory ganglia, the optic lobes, the corpora striata, 

 and the optic thalami, be removed, the animal loses the special senses of smell and sight 

 and the intellectual faculties, there is a certain amount of enfeeblement of the muscular 

 system, but voluntary motion and general sensibility are retained. There can be no 

 doubt upon these points. As far as voluntary motion is concerned, an animal oper- 

 ated upon in this way is in nearly the same condition as one simply deprived of the 

 cerebral hemispheres. There are no voluntary movements which show any degree of 

 intelligence, but the animal can stand, and various consecutive movements are executed, 

 which are entirely different from the simple reflex acts depending exclusively upon the 

 spinal cord. The coordination of movements is perfect, unless the cerebellum be re- 

 moved. As regards general sensibility, an animal deprived of all the encephalic ganglia 

 except the tuber annulare and the medulla oblongata undoubtedly feels pain. This has 

 been demonstrated in the most conclusive manner by Longet, and has been shown even 

 more satisfactorily by Vulpian. In rabbits, rats, etc., after removal of the cerebrum, 

 corpora striata, and optic thalami, pinching of the ear or foot is immediately followed by 

 prolonged and plaintive cries. Both of the experimenters referred to insist upon the 



