66 



nal cord is made'on the whole part supplying nerves to the anterior 

 limbs, then it is found that sensibility is lost in both these limbs, 

 and that it is only slightly diminished in the posterior limbs. 



llth. If the same operation is done as in the preceding expe- 

 riment, and afterwards if a transversal division is made on one 

 of the lateral halves, in the place where it is separated from the 

 other, then it is found that the posterior limb on the side of the 

 transversal section remains sensible, and that the other posterior 

 limb loses its sensibility. 



These experiments prove very clearly that the sensitive ner- 

 vous fibres are crossed in the spinal cord. The 9th, 10th, and 

 llth, demonstrate directly the crossing. In these experiments 

 the crossed fibres are all cut, and sensibility is lost. This fact 

 appears to prove that all the sensitive fibres cross each other ; 

 but it will be easily understood that on account of the loss of 

 blood, and of the general diminution of sensibility produced by 

 the excessive pain of the operation, if there are some fibres 

 which remain without crossing, they are insufficient to give 

 sensations. 



As to the experiments consisting in transversal sections of a 

 lateral half, they prove that sensibility is much diminished in the 

 side of the body opposite to that of the section ; consequently 

 they prove also that there is a crossing of a great part of the 

 sensitive fibres. 



The fact that transmission of impressions made on one side of 

 the body takes place, at least for a great part, in the opposite 

 side of the spinal cord, is proved evidently by the eight first 

 experiments, but much more by the 7th and the 8th experiments 

 in which it is found that, after a section of a lateral half of the 

 spinal cord, sensibility remains on the same side, and that it is 

 nearly entirely lost after a second section of the other lateral 

 half in another place. 



If most of the nervous sensitive fibres are crossed in the 

 spinal cord, then it is not exact to admit that the crossed paraly- 

 sis of sensibility in cases of diseases of the brain, is explained 

 by the crossing of fibres which exists in the pons Varolii and in 

 other parts of the encephalon. Many opinions have been pro- 

 posed as regards the place where the sensitive nervous fibres 

 make their crossing in the encephalon. According to some pa- 



