On Rickets 313 



be tied above and below to a young and growing 

 tree, yet so that the tree is not strained by the string, 

 as is shown in Plate IV., Fig, 7, every one will admit 

 that the said tree will be bent as it grows, as in Plate 

 IV., Fig. 8. And the mathematical proof of this is 

 obvious, for if any line is elongated while its extremi- 

 ties remain fixed, the line will cease to be a straight 

 line, and this is what happens to the bones in this 

 disease. 



And this may be further confirmed by the fact that 

 the bent bones always have their concave side turned 

 towards the attached muscle, just as a bow and its 

 string, as may be seen in the case of the tibia, which 

 is prominent and convex in front, but concave on 

 the posterior side which looks towards the muscles ; 

 and the same is the case with the other bones — no 

 invalid argument that the bones are bent by the 

 muscles just as the bow by its string. 



And this gives us the reason why quacks regularly 

 and successfully apply friction to the concave and 

 not to the convex side of the bones ; for by the more 

 plentiful supply of nutritious juice which such friction 

 calls forth, the muscle situated on the concave side 

 of the bone is nourished and grows, so that it is not 

 surprising that when the string is elongated the bone 

 strained and bent by it is also relaxed and becomes 

 straighter. And this is the reason why persons who 

 have recovered from this disease grow very much in 

 height ; for the bones not only grow as in other 

 persons, but in their return from curvature to straight- 

 ness are more elongated. 



The spine is also variously bent, partly inwards, 

 partly outwards ; and this arises from the various 

 position of the muscles in different parts of the spine, 

 for the spine in its upper part is curved inwards by 



