791 



mean error of the middle-value for o = ±: 12.604 and 7i = 5 was 

 determined at ± 5.637; llie absolute middle-value for the deaf-mute 

 cases thus became Md = 15.963 ± 5.637, and so appeared to lie 

 between 21.600 and 10.326. 



No important difference between right and left was stated. 



If we now compare the two categories, the question arises: what 

 do these middle-values Mn and Md prove ? 



The limits of J)/„ and Aid overlap, so they do not prove a 

 difference in variability between the normal and the deaf-mute 

 cases. This would be otherwise if the hij^hest value of Md had 

 been smaller than the lowest of M„. In this latter case we might 

 state that in the deaf and dumb the number of giant cells in the 

 Heschl convolution is considerably reduced and this diminution 

 might be ascribed to the deaf-mutism. The calculations, however, 

 show that we are not justified in drawing this conclusion. 



Thus the variability of the number of giant cells in the Heschl 

 con\olution is very great. Compare e.g. the case n. F. 1., in which 

 not a single giant cell is found, with the case n. A. r., where the 

 number is relatively very great. We get the impression that the 

 number of giant cells in the cortex of this region is in the deaf 

 and dumb occasionally considerably less than in normal people; on 

 the other hand the cases n. F. 1. and d. West 1. weaken this 

 impression again. 



The extent of the variability we find expressed in a table given 

 by JoHANNSEN ^). In this table the play, left to the variations, is 

 given, and it is stated that 99.7 7o of the cases will fall within 

 the space S = M ± S (J. 



So we get for the normal cases : 



S„ = M„ ± 3ö= 24.111 ± 3 X 14.414 = 24.111 ± 43.242, so that S„ 

 is the space between 67.353 and 0. 



In the deaf-mute cases we find 



Sd=Md± 3rt 3= 15.963 ± 3 X 12.604 z= 15.963 ±37.812, 



the space ranging from to 53.505; the upper limit lies somewhat 

 lower than with the normal cases. 



From the preceding investigation we may conclude: 



1. that the variability of the number of giant cells in the Heschl 

 convolution is very great, 



1) JoHANNSEN, 1, c. Fünfte Vorlesung. 



