INTRODUCTION 



17 



measured by the parallelograph, an instrument designed to record the 

 projection of any given transverse axes established at the two ends, and 

 projected upon a plane at right angles with the main axis of the bone 

 (Fig. 11). If, for example, in the case of the femur, the axis of the head 

 and neck be indicated by a knitting needle (Ai), fastened to the bone by 

 wax or plastilina, and if at the other end the axis of the condyles be 

 similarly shown by a needle placed tangent to the condyles upon their 

 ventral surfaces (A 2 ), the torsion of this bone would be indicated by the 



Fig. 10. — Stationary goniometer of Martin. (Manufactured by Hermann; Zurich.) 



angle made by these two needles, when the bone is viewed "end on;" in 

 other words, when these two axes are projected upon a plane perpendicular 

 to the shaft. (For an illustration of this, cf. Fig. 32). 



To actually draw and measure such an angle, a bone is taken, and the 

 cross axes to be compared are indicated by the needles, after which the 

 bone is placed in an osteophore, which holds it rigidly in a vertical 

 position. A retort stand, equipped with a heavy iron clamp, capable of 

 movement in several directions, serves as the osteophore. This appa- 

 ratus, including the vertically placed bone with the two needles, is to 

 be placed upon a large sheet of paper, so fastened as to prevent slipping. 



