MUSCULAR SENSATION. 401 



etc. The subject has received most accurate investigation from Head, 1 who 

 has shown that there is an intimate nervous connection between the internal 

 organs and definite areas of the skin, manifested by pain and tenderness 

 appearing in sharply-localized regions on the surface when definite organs 

 become disordered. He has also demonstrated that disorders of the thoracic 

 and abdominal viscera not only produce pain and tenderness on the surface of 

 the body, but also cause pain and tenderness over certain areas of the scalp. 

 Head is inclined to explain the topographical association of skin-tenderness 

 with visceral disorders by the assumption that the nerve-supplies of the parts 

 so related find their origin within the same segment of the spinal cord. The 

 sensory result of visceral irritation may be summarized in the following way : 

 " When a painful stimulus is applied to a part of low sensibility in close cen- 

 tral connection with a part of much greater sensibility, the pain produced is 

 felt in the part of higher sensibility rather than in the part of lower sensibility 

 to which the stimulus was actually applied." 



Certain transferred pains are explained by Meltzer 2 in the following man- 

 ner : An inflamed or irritated organ originates a succession of sensory 

 stimuli, which do not awake consciousness because they are continuous. 

 There is, nevertheless, a summation of such irritations within the central 

 organ which elevates its plane of irritability to such an extent that sensory 

 impulses reaching the implicated nerve-centre from any part of the body 

 arouse it above the threshold of consciousness and give rise to sensations 

 which are referred to the seat of peripheral inflammation or constant irrita- 

 tion. For example, the subject of a mild alveolitis may feel in the teeth a 

 stronger pain than is felt in the nose when a concentrated solution is thrown 

 into the latter organ. 



That this transferred localization may characterize other sensations than 

 those of pain has been definitely observed by Obersteiner, 3 who found that in 

 patients suffering from certain central nervous lesions tactile irritation of a cer- 

 tain point on the skin was referred by them to some other part of the body, 

 usually the corresponding point on the other side. He designated this trans- 

 ference of sensation by the term allochiria, meaning a confusion of sides. 



4. Muscular Sensation. — Closely allied to common sensation, if not a 

 part of it, is muscular sensation. If two weights are to be compared, we 

 naturallv do not lay them on the skin to determine their pressure-difference, 

 but we lift and weigh them in the hands, and experience shows that a much 

 more accurate estimate may thus be made. 



We undoubtedly have a keen perception of the tension of a muscle, and 

 therefore of the amount of resistance against which it is contracting. This per- 

 ception may be the outcome of a direct consciousness «>)' the amount of motor 

 energy sent out from the motor cells, or it may be due to the inflow of sensory 

 impulses which show the tension to which the muscles have been subjected. 

 The latter view has more to be said in its favor. 



1 Brain, 1893-4. 



* S. J. Meltzer: Philadelphia Medical Journal, August 5, 1899, p. 12. 3 Brain, 1881. 



Vol. II.— 2G 



