SURGICAL APPLIED ANATOMY. [Chap. n. 



splintering than does the external. There are many 

 reasons for this. The internal plate is not only 

 thinner than the external, but is so much more 

 brittle as to receive the name of the "vitreous table." 

 A force applied to the external table may be extremely 

 limited, and produce, as in a sabre cut, but a 

 limited lesion. As the force, however, travels 

 through the diploe it becomes broken up, and 

 reaches the inner plate as a much more diffused 



form of violence. This 

 is especially the case 

 when parts of the 

 outer table are driven 

 in. Then, again, the 

 internal plate is a 

 part of a smaller 

 curve than is the ex- 

 ternal plate ; and, 

 lastly, Agnew assigns 

 a reason for the 

 greater vulnerability of the inner plate that has 

 reference to the general yielding of the bone. In 

 Fig. 5, AB represents a section of a part of the 

 vault through both 

 tables, and c D and 

 E F two vertical and 

 parallel lines. Now, 

 if force be applied 

 to the vault between 

 these parallel lines, 

 the ends of the arch, 

 A B, will tend to be- 

 come separated, and 

 the whole arch, yielding, will tend to assume the curve 

 shown in Fig. 6. In such case, the lines c D and E F 

 will converge above and diverge below (Fig. 6), so 

 that the violence would tend to force the bone 



Fig. 6. 



