THE SENSORTAL POWER. 143 



experiments lately performed by Weinhold. He remo- 

 ved the brain and spinal marrow of a cat, and after all 

 signs of life had disappeared, he filled up the cranium 

 and vertebral canal with an amalgam of mercury, zinc, 

 and silver. The effect was, that the animal soon gave 

 signs of life ; it raised its head, opened its eyes, looked 

 steadily, attempted to walk, and endeavoured to rise af- 

 ter frequently tailing down. In the mean time, the cir- 

 culation was renewed, and the secretion of the gastric 

 juice seemed more abundant than ordinary. The ani- 

 mal heat was also re-established. This gentleman also 

 remarked, that the extremities of a divided nerve gave 

 sparks when brought together. 



Emily. A most marvellous experiment truly, and not 

 without its practical utility too, for perhaps in time, some 

 more perfect composition may be found which will re- 

 store even the creature's mousing propensities, and in 

 short, make it once more, sound and healthy as ever. 



Dr. B. We must now turn our attention to the sen- 

 sorial power. In regard to sensation, we know no more 

 than that a certain series of changes invariably precede 

 its appearance, and that its seat is somewhere in the brain. 

 We can define it only by mentioning these changes which 

 has been already done. In the first place an impression 

 is made from the external world, upon an organ ex- 

 pressly destined to receive, ,and prooerly modify it. 

 By means of a nevre in connection with this organ, the 

 impression is communicated to the brain. Lastly, it is 

 received into the brain, and recognized by the mind. 



Emily. Is it necessary, Dr. B., that each of these, 

 stages must be passed through, in order that sensation 

 rnay take place ? What would be the effect of irritating 

 the nerve of vision, for instance ? 



Dr. B. The effect would be that neither motion 

 nor sensation would be produced. If the organ, nerve 

 or part of the brain whither the impression is carried, be 

 destroyed or injured, no sensation will be produced. 



