CHAP, ii.] THE BRAIN. 805 



same side ; but cases have been recorded in which the muscular 

 sense in company with other sensations, seemed to be affected 

 on the crossed side ; it must be remembered however that it 

 is very difficult to appreciate a deficiency of muscular sense 

 mingled with deficiencies in other sensations, and we should 

 d priori expect the muscular sense to run parallel with motor 

 impulses. 



The clinical histories of diseases of the spinal cord in man 

 bring to light in a fairly clear manner a fact of some importance, 

 namely, that the several impulses which form the bases of the 

 several kinds of sensations, of touch, heat, cold, and pain, and 

 of the muscular sense, are transmitted along the cord in different 

 ways and presumably by different structures. For disease may 

 impair one of these sensations and leave the others intact. Thus 

 cases of spinal disease are recorded, in which on one side of the 

 body or in one limb ordinary tactile sensations seemed to be little 

 impaired, and yet sensations of pain were absent ; when a needle 

 was thrust into the skin no pain was felt, though the patient was 

 aware that the needle had been pressed upon the skin at a par- 

 ticular spot ; and conversely in other cases pain has been felt 

 upon the insertion of a needle, though mere contact with or 

 pressure on the skin could not be appreciated. Again, cases are 

 recorded in which the skin was sensitive to touch or pain, but 

 not to variations of temperature ; it is further stated that cases 

 have been met with in which cold could be appreciated but not 

 heat, and vice versa; and there are some facts which point to 

 sensations of pain being more closely associated with those of 

 heat, and tactile sensations with those of cold, than those of pain 

 with those of touch or those of heat with those of cold. Cases 

 of spinal disease are also recorded in which the muscular sense 

 appeared to be affected apart from other sensations. We shall 

 return to these matters later on in dealing with the senses ; we 

 refer to them now simply as shewing that disease, limited as far 

 as can be ascertained to the spinal cord, may affect the several 

 sensations separately, and therefore as suggesting that the sev- 

 eral kinds of impulses, forming the bases of the several kinds of 

 sensation, are transmitted in different ways and follow different 

 4 paths ' along the spinal cord. 



When however we appeal to clinical histories or indications 

 as to the several paths within the spinal cord taken by these 

 several impulses, the answer is a most uncertain one, as indeed 

 might be expected from the too often diffuse character of the 

 lesions of disease ; and it is perhaps not too much to say that 

 no satisfactory deductions at all can be made. 



509. Whether then we turn to experiments on animals or 

 to the study of disease, the teachings with regard to sensation, 

 in contrast to those with regard to voluntary movement, are in 

 the highest degree uncertain and obscure. A few general reflec- 



