Franklin P. Mall 397 



the humerus, the styloid process still deflects when the elbow is flexed 

 and in case it is greater it is turned in. Braune and Kyrklund's few 

 ca^es (nine in number) seem to bear out these statements, but they are 

 by no means always borne out by my records. The sigmoid cavity does 

 not hug the trochlea closely and the slight rotation of the coracoid and 

 olecranon processes may be sufficient to account for my figures. Fur- 

 thermore, the inequalities in diameter and form of the two conical sur- 

 faces of the trochlea may cause sufficient shifting to counteract a slight 

 difference between the angles of the humerus and ulna. This is already 

 indicated when the points below the epichondyles through which the axis 

 passes are determined. One of them is usually extended into a line 

 several millimeters long showing that the section of the cone of the 

 trochlea is not circular on that side. Even my averages do not confirm 

 Braune and Kyrklund's notion. In my 89 specimens, the average of 

 the angle of the humerus is 82.5 degrees, and of the ulna 86.5 degrees, and 

 yet the styloid process still deflects .5 degree when the arm is flexed to the 

 maximum. This, of course, is when the elbow is flexed to 39 degrees, 

 and could it be flexed to the styloid process should turn in about 3 

 degrees. In general the irregularities of the surfaces of the elbow joint 

 fully neutralize the fine difference between the angles of the humerus and 

 ulna and only in a general way is the assertion of Braune and Kyrklund 

 correct. In about three-fourths of my measurements the angle of the 

 ulnais greater than that of the humerus, while in Braune and Kyrklund's 

 measurements (but one-eighth as many) they w^ere just the opposite. 



The extent of motion of the elbow from flexion to extension gires some 

 interesting results. It is well known that the extent of movement in the 

 joint of children is much greater than that of adults, and artists often 

 try to express this in the arms of children and young, delicate girls^ I 

 have often observed this difference in examining arms of infants in the 

 dissecting rooms. In fact, in numerous specimens which I have exam- 

 ined not a single infant's arm was found in which the elbow could not 

 be hyperextended. The measurements from the adult arm which I 

 have made give equally interesting results, for they point towards a 

 sexual difference. The following table gives the degree of extension of 



Degrees of extension 155° 160' 165° 170° 175° 180° 185° 190° 195° 



Number of males 1 6 19 14 14 6 3 1 .. 



Number of females 2 6 7 5 2 1 2 



Total 1 6 21 20 21 11 5 2 2 



89 measurements. The straight arm is 180°. It is evident that 

 the female arm is straighter and more frequently hyperextended than the 



