138 DISCOVERIES OF MR. BELL. 



and watch the effect. The spinal canal was laid open 

 several times in rabbits, and the posterior roots of the' 

 nerves of the lower extremities were divided. The an- 

 imal's motions were not impeded, but the extremity was 

 ascertained to be utterly destitute of sensation. It might 

 be pinched, cut, pricked, or otherwise irritated, without 

 giving the creature the slightest degree of pain. In the 

 next experiments, the anterior roots were divided and 

 the posterior left undisturbed. The limb now lost all 

 power of motion, while its sensibility remained unimpair- 

 ed. 



Emily. The spinal nerves are in reality, then, dou- 

 ble nerves ; but do they continue distinct throughout 

 their whole course, even to their extremities ? 



Dr. B. They continue distinct, but we are not able 

 to distinguish them on account of their very intimate con- 

 nection. Each nerve, when minutely examined, will be 

 found to be an aggregate of very delicate filaments, bound 

 up in a common cellular envelope. These filaments are 

 for the purpose, either of sensation, or motion, and they 

 remain distinct from one another in their whole course, 

 from their extremities in the parts which they supply 

 with nervous power, through the spinal marrow, to their 

 termination in the brain. 



Emily. And this too, without any interference with 

 each other ! no derangement of each other's functions ! 

 Truly there is no end to the wonders displayed in the 

 construction of the human frame. 



Dr. B. Mr. Bell now thought that this view of the 

 functions of the nerves would be confirmed, if after 

 tracing the distinct columns of nervous matter in the 

 spinal marrow, into the brain, he should find nerves of 

 motion connected with the anterior column, and nerves 

 of sensation, with the posterior column. This fact was 

 also satisfactorily established. Again, he saw that one 

 nerve of the brain, the fifth, had a close resemblance to 

 fhe spinal nerves, being connected to the brain by two 

 roots, and he concluded that like them, it was a nerve of 



