SYSTEMATIC ANALYSIS OF THE BODY. 



43 



foot is prevented from acting 

 on the head. When unexpect- 

 edly a person steps down upon 

 the ground with the limbs 

 straight, a shock is felt that a 

 bent or flexed state of the limbs 

 would have prevented. The ir- 

 regular form of the pelvis and 

 the hip-joint, not being directly 

 under the spinal column, nor m 

 its plane, as well as the curva- 

 tures of the spinal column, as- 

 sist in the same result of pre. 

 serving the brain from receiving 

 jars. 



72. THE CENTRAL POR- 

 TIONS OF THE BONES ARE CON- 

 STRUCTED either as canals, or 

 as cells, like those of a sponge, 

 filled with marrow, which 

 serves to make the framework 

 lighter, as a stock of food in 

 time of need, and especially to 

 deaden the jars that are pass- 

 ing upward to assault the 

 brain, and annoy it. 



FIG. 67. 



Fig. 67 is a plan to represent 

 how the force with which the 

 foot strikes the ground is sent off 

 in the directions a, b, c, d, e, so 

 that but little reaches the head. 

 Those are but a few of the points 

 of dispersion. 



73. Illus. If in sickness, or from exposure to starva- 

 tion, the marrow of the bones is exhausted, each step, 

 unless taken with great care, jars the brain very un- 

 pleasantly. 



74. UNDER THE BRAIN, and between it and the 

 skull, there is a sponge-like cushion, the spaces of which 

 are filled with a watery fluid ; while a portion and con- 

 tinuation of the same extends down around the spinal 

 cord, or large bundle of nerves that nearly but not 



Describe Fig. 67. 72. How are ? 73. What Illus. to show value of marrow ? 

 74. What is ? 



