SENSIBILITY OF THE BONES.' 



place in old persons the bones are furnished with too 

 little animal matter. Hence, in falling, old people are 

 more liable than young persons to break their bones. 



Emily* \\hat are tiie earths found in the composi- 

 tion of bones ? 



Dr. B. If we except a small portion of two or three 

 other salts, the earthy substance of the bones, is almost 

 entirely phosphate of lime constituting about one half 

 of the whole bone. This earthy salt, you know, is in- 

 soluble in water, and will bear a very high temperature 

 without decomposition. Hence, as might be supposed, 

 bones are the most durable of all parts of an organized 

 body, and capable of resisting, for an astonishing length 

 of time, the influence of external agents. Bones are 

 now found in the earth by geologists, of animals that 

 must have perished long before the last revolutions that 

 have changed the surface of our globe. The animal 

 substance of bones is probably cartilage, at least it very 

 nearly resembles that substance with a small quantity 

 of jelly and oil contained in the spongy substance. 



Emily. The bones being one half mere earth, can- 

 not, I should suppose be very sensible, and yet we often 

 hear people complain of pain in their bones. 



Dr. B. This is probably an illusion, for bones in & 

 healthy state may be sawed, cut, scraped, or broken 

 without causing the least pain, and therefore it has been 

 considered by some physiologists, that they possess na 

 nerves. 



Emily. Is it known that they possess blood-vessels,, 

 and absorbents ? Do they bleed when cut or broken ? 



Dr. B. The latter fact is not necessary to prove the 

 existence of blood-vessels. Though we can see no 

 traces of blood-vessels in the bones, yet many observa- 

 tions and experiments, confirm us in the belief beyond 

 all manner of doubt, that the bones are organized bodies, 

 and of course require arteries, veins, absorbents and- 

 serves. 



Emily.' I should like to hear some of these expert 



