300 THE AMERICAN NATURALIST. 
rises 3% inches above the spur and extends downward exter- 
nally tothe protractor scale. Theright end of the needle should 
terminate in an eye, through which the spur passes ; the figure 
represents the trial needle not thus arranged. 
The post B is movable ; its base slides in the groove of the 
base board and is held in position by a thumbscrew. The top 
is provided with a strip of steel 3 inches in length. The strip 
is provided with saw teeth that engage the head and great 
trochanter of the femur at the same time (or both condyles), 
for it is pivoted at its center and stands in the plane of the long 
axis of the bone. This strip is fixed in an exactly vertical 
position, and the protractor is exactly horizontal in relation 
to it. 
The torsion of any long bones can be measured with this 
instrument. The axis of each end is first indicated in pencil ; 
the spur of the post 4 is then engaged with the lower portion 
of the axial line at one end of the bone; the post B is pushed 
to the left until the strip of steel is in contact with the axial 
line of that end of the bone. With the left hand the needle 
on post 4 is adjusted so that the arms are in the plane of the 
axis of the left end of the bone, the end of the needle points 
to the degree of torsion on the protractor. 
The operation can be performed rapidly and with accuracy. 
As the bone can be turned end for end and remeasured in 
other positions, we have a ready means of making control 
measurements. In practice I have not found it necessary to 
use any support for even fragile bones, but to insure against 
accident to such material it is advisable, perhaps, to have a 
narrow table between the posts of the apparatus, which will 
not support the bone but simply prevent its falling far enough 
to injure it. 
The apparatus can be made by any skilled mechanic. The 
model figured here was made for me by a graduate student of 
anthropology, Mr. W. C. Farabee, at Harvard University. 
PEABODY MUSEUM OF 
AMERICAN ARCH;EOLOGY AND ETHNOLOGY. 
