in. 2. 1. 11. OF VOLITION. 339 



published some successful cases of the use of mercurial oint- 

 ment. See Colica Saturnina, I. 2. 4. 8. See Class III. 2. 1. 4. 

 Dr. J. Alderson has lately much recommended the leaves of 

 rhus toxicodendron (sumach,) from i. gr. to iv. of the dried 

 powder to be taken three or four times a day. Essay on Rhus 

 Toxic. Johnson, London, 1793. But it is difficult to know 

 what medicine is of service, as the movements of the muscles 

 must again be learned, as in infancy, by frequent efforts. 



11. Paraplegia, A palsy of the* lower half of the body divid- 

 ed horizontally. Animals may be conceived to have double bo- 

 dies, one half in general resembling so exactly the other, and 

 being supplied with separate sets of nerves; this gives rise to 

 hemiplegia, or palsy of one half of the body divided vertically; 

 but the paraplegia, or palsy of the lower parts of the system, 

 depends on an injury of the spinal marrow, or that part of the 

 brain which is contained in the vertebrae of the back; by which 

 all the nerves situated below the injured part are deprived of 

 their nutriment, or precluded from doing their proper offices; and 

 the muscles, to which they are derived, are in coiibequcnce dis- 

 obedient to the power of volition. 



This sometimes occurs from an external injury, as a fall from 

 an eminence; of which I saw a deplorable instance, where the 

 bladder and rectum, as well as the lower limbs, were deprived of 

 so much of their powers of motion, as depended on volition or 

 sensation; but I suppose not of that part of it, which depends on 

 irritation. In the same manner as the voluntary muscles in hemi- 

 plegia are sometimes brought into action by irritation, as in 

 stretching or pandiculation, described in Sect. VII. 1. 3. 



But the most frequent cause of paraplegia is from a protuber- 

 ance of one of the spinal vertebrae; which is owing to the innu- 

 trition or softness of bones, described in Class I. 2. 2. 17. 

 The cure of this deplorable disease is frequently affected by the 

 stimulus of an issue placed on each side of the prominent spine, 

 as first published by Mr. Pott. The other means recommended 

 in softness of bones should also be attended to; both in respect 

 to the internal medicines, and to the mechanical methods of sup- 

 porting, or extending the spine; which last, however, in this case 

 requires particular caution. 



12. Somnus. In sleep all voluntary power is suspended, see 

 Sect. XVIII. An unusual quantity of sleep is often produced 

 by weakness. In this case small doses of opium, wine, and 

 bark, may be given with advantage. For the periods of sleep, 

 see Class IV. 2. 4. 1. 



The subsequent ingenious observations on the frequency of 



