162 



ADOLF H. SCHULTZ 



relative number of cases possessing humeri of equal and differ- 

 ent lengths and the average differences of the individual asym- 

 metries, shows that 32.5 per cent of white males have a longer 

 left humerus. It also demonstrates that in white males the 

 differences in favor of the left side are on the average greater 

 than those on the right, which is not the case in the other 

 groups. The greatest absolute asymmetry occurred in a negro 

 whose right humerus exceeded the left in length by 23 mm. 



TABLE 3 



Averages, standard deviations, variation-coefficients, their probable errors and 

 ranges of variation for the position index of the insertion of the pectoralis major 

 m uscle 



Whites 



Negroes 



M ± E {M) 



a± E (o-) 



28. 37 ±0 17 1.5o±0.12 



■28.50±0.16 1.49±0.11 



28 43±0 11 1 o2±0.08 



26 37±0.35 1.74±0 25 



26 35 ±0.56 2.73±0.39 



26.36±0.33 2.29±0 23 



28 27±0.19 1.75±0.14 



27.99±0.17 1 57±0.12 



28.13±0.13 1 67±0 09 



26 82 ±0 32 1 89±0 23 



26 45±0 3l| 1.82±0 22 



26.6]±0 22 1.86±0.16 



E (v) 



5.46±0.41 



5 23±0.40 

 5.35±0.28 

 6.59±0.94 



10.34±1.48 

 8.67=t0.88 



6.18±0.48 

 5.61=t0.44 

 5.94±0.33 

 7.05±0 85 



6 89±0.83 

 6.99±0.59 



MINI- MAX- 

 MUM MUM 



24.3 

 25.3 

 24.3 

 21.9 

 21.3 

 21.3 



26.1 

 25.1 

 25.1 

 23.1 

 22.3 

 22.3 



31.3 

 31.8 

 31.8 

 28.3 

 29.5 

 29.5 



35.2 

 32.6 

 35.2 

 30.9 

 30.3 

 30.9 



The averages and the conditions of variability of the index of 

 position for the middle of the insertion of the pectoralis major 

 muscle are given in table 3. This index differs in the entire 

 material between 21.3 and 35.2. Expressing this in terms of the 

 mechanics of levers, one can state that in the adult the lifting 

 arm of the musculus pectoralis major is related to the carrying 

 arm — the length of the humerus — in a ratio varying from 21.3: 

 100 to 35.2: 100. In other words the relation of the lever arms 

 may differ by almost 14 per cent of the length of the carrying 

 arm, and this expressed in an absolute number equals on the 

 average about 45 mm. A different proi:)()rtion of the lever arms 

 influences not onlv the force of the muscle hut also the movement 



