278 REVIEWS. 



The fourth lecture commences by the expression of the author's 

 hope that he shall be able to show, that the various sensitive impressions 

 of touch, of pain, of temperature, of muscular contraction, &c. are trans- 

 mitted by conductors which are quite distinct from one another, and 

 so much so, that the conductors of painful impressions, for instance, 

 are no more able to convey other kinds of impressions than to trans- 

 mit the impulses of the will to muscles. It is to be regretted that Dr. 

 Brown- Sequard has not, in these lectures, given very fully all his reasons 

 for adopting this view. The Muds of sensitive impressions which he 

 believes to be furnished with distinct and separate conducting fibres, 

 are the sensations of touch, tickling, pain, heat, cold, and the pe- 

 culiar sensation which accompanies muscular contraction. It is 

 obvious that in seeking to interrogate nature upon points so delicate 

 and refined as these, experimentation upon the lower animals can give 

 no satisfactory answer ; pathological cases, scrutinised with truthful- 

 ness and care, can alone yield accurate information upon these topics. 

 Hence it is that Dr. Brown- Sequard, with an earnest desire to obtain 

 light from every source, with a view to the elucidation of these im- 

 portant problems, appeals to the many medical men who may peruse 

 his book, and who have yearly opportunities of seeing numbers of 

 patients, whose cases may throw important and often decisive, light 

 upon the questions discussed in his paper. Those persons whose in- 

 terest in science and love of mankind dispose them to respond to 

 this appeal, and not to allow to pass unrecorded such cases, as may be 

 the means of tending to settle what is yet undecided in these ques- 

 tions, may add a thousand fold to the interest and value of such cases 

 as they may describe, by adopting one simple means of estimating, with 

 precision, the comparative capability possessed by different parts, of 

 appreciating the sensations of tickling, pricking, touch, heat, &c. In 

 the normal state, different portions of the surface are very variously 

 susceptible of these sensations; the tickling sensation, produced by light 

 brushing of the surface with a camel's hair pencil, is more felt around 

 the mouth, than over the nose ; along the front of the forearm, than 

 in the palm, or along the fingers : the feeling of a light shock or im- 

 pulse, like the pulsation of an artery, is much more distinctly per- 

 ceived by the tips of the fingers than by the knuckle, the lips or the 

 tip of the tongue ; thus, if a thin tube of vulcanised indian-rubber be 

 quite filled with water and tied at both ends, an impulse, produced by 

 letting a little hammer fall on one end, is felt at the other by the 

 finger, when the same cannot be appreciated by the lips, tongue, and 

 other parts ; if, on the contrary, the whole hand be held under water 

 and a gentle current be made to pass from a pipe through the water, 

 the striking of the current on the hand is felt at a greater distance 

 from the pipe, by the back of the hand, than by the palm. If ether, 

 or spirit, be applied to the surface and a draft of air made to play 

 upon the parts, the cold produced will be felt very differently by dif- 

 ferent parts of the body ; if a needle or pin be made to pass through 

 a small disk of cork so that a very little of the point projects, the 



