Dr. Ritchie's Rcplij to Mr. Uainey. 57 



marrow by stimulation, produce the same phaenomenon. In 

 men with excitable debihty of the nervous system any unfore- 

 seen sensation, sound, touch, or mechanical shock produces a 

 general start. So also in men who, by stimulation of the ge- 

 nitals, and thereby of the spinal marrow, or by other causes, 

 have acquired an excitable debility of the spinal marrow. 

 We may here cast a glance at the nature of nervous irrita- 

 tion. All nervous stimuli may induce in succession three con- 

 ditions. First, excitement, in which the powers appear still 

 uninjured. Second, in proportion as the excitement is re- 

 peated, excitable debility. Third, atonic debility. 



" 4. A local violent excitation of a sensitive nerve, may by 

 the violence of the centripetal excitation of the brain and spi- 

 nal marrow, induce twitchings and tremblings, as after a se- 

 vere local burn, in tooth-drawing, &c. 



" 5. Local stimulations of the nerves by linflammation or 

 tumours, often also produce general spasms, or even epi- 

 lepsy. 



"6. The irritation of the spinal marrow, originating from 

 local sensorial excitement, may in violent injuries be so great, 

 that the movements are constant, and continue even without 

 touching. This irritation of the spinal marrow resulting from 

 severe local nervous injuries, is the tetanus traumaticus. 

 Every severe irritation of the spinal marrow generally is teta- 

 nus, whether produced by narcotic poisoning or locally and 

 indirectly. I have here shown how the production of tetanus 

 traumaticus is to be explained by simple empirically deter- 

 mined facts. 



" 7. The severe irritation of the sympathetic nerves of the 

 intestinal canal also excites by acting back on the central 

 parts general spasms ; and thus the cramps in sporadic cholera, 

 as well as the convulsions in the diseases of the viscera in 

 chiklren, are to be explained. 



[To be continued.] 



XIV. Reply to Mr. Rainey's Communication in the Phil. Mag. 

 for December 1836. By the i?^u. William Ritchie, LL.D.^ 

 F.R.S., Professor of Natural Philosophy in the Royal Insti^ 

 tution of Great Britain and in the University of London. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



TT is not with any wish of having the last word in the discus- 

 sion of the principles at issue between Mr. Rainey and myself, 



but simply with a desire of establishing scientific truth on a 

 Third Series. Vol.10. No. 58. Jaw. 1837. I 



