Page:Brain Volume 31 Part 3.pdf/44

 Unfortunately, the size of the area on the hand did not permit of the complete application of tests for shape. It was found that even a circle, a square or a triangle, cut out of wax so that all lay entirely within a 4 cm. square, could not be distinguished with certainty on the dorsal surface of the sound hand. But, although the answers were wrong as regards the shape, H. had a definite sensation of pressure on a circumscribed surface, a surface with borders and angles. On the affected hand, the sensation was one of pure pressure accompanied by no idea that the object by which the pressure was produced had any shape. Thus, on June 22, it was noted that on the back of the left hand there was a complete absence of any element of shape in the sensations. Pressure was experienced, and this was well localized, but there was nothing to indicate that the body producing the pressure had any shape. But on the sound side there was a distinct impression of form, chiefly of angles here and there, though the total shape could not be perceived correctly.

When a very large surface was applied, H. thought it seemed to him large, because he had a visual picture of his hand on which he had certain points of reference, such as the first and second metacarpal bones with their tendons. He imagined the object was large, because he perceived a sensation from both these widely separated places. But this failed entirely if both spots could be touched strictly simultaneously when the large object was applied to the skin.

In some of the observations in which the skin was stimulated successively with compass-points, the sensation produced was not so much one of "twoness" as of rocking or pushing on the skin. This led us to test whether the affected area was especially sensitive both to progressive movement over the skin and to rotatory movement of a round object in which the stimulated area of the skin remained the same.

Slight movements were readily appreciated on the affected side, but we could not detect any definite difference in sensitiveness between the two hands.

Head and Sherren ([17] p. 214) were able to show that perfect recognition of passive movement of the joints was possible when the