GROWTH OF BONE. 451 



which may occur in the bones in morbid conditions, for 

 every one of these new-formations finds a certain proto- 

 type in the normal development of bone. 



All the larger bones grow, as is well known, in two 

 directions. This is most simply shown in the long bones, 

 which gradually increase in length and thickness. The 

 growth in length takes place from cartilage, that in 

 thickness from periosteum. But a flat bone also is in- 

 vested on the one hand with cartilaginous parts or their 

 equivalents (sutures) and on the other with membranes 

 which correspond to periosteum. A growth from carti- 

 lage and a growth from periosteum can therefore be 

 distinguished in every bone. This furnishes us with a 

 plan of the development of long bones, which is found 

 even in the writings of Havers, and according to which 

 the new layers of bone incapsulate the old ones, and 

 every more recent layer is not only wider but longer 

 than that next above it in age. Every new layer of 

 osseous substance which is formed out of periosteum is 

 longer (higher) than the one immediately preceding it, 

 inasmuch as new layers of perichondrium are being 

 continually converted into periosteum. At the same 

 time every new layer of osseous substance which grows 

 out of cartilage is broader (thicker) than that which went 

 before it, inasmuch as every new layer of the (growing) 

 cartilage which proceeds to ossification surpasses its pre- 

 decessor in breadth (thickness). The growth from car- 

 tilage, however, can only take place in the direction of 

 the extremities of the bone, inasmuch as the cartilage 

 of its diaphysis is, at a very early period of intra- uterine 

 life, so completely ossified,* that no cartilage remains ex- 



* This complete ossification in long bones is not confined to intra-uterine life, but 

 every new layer of cartilage which grows out of the terminal cartilage up to the 

 age of puberty ossifies (when matters follow a normal course) throughout its whole 

 thickness, so that no cartilage remains at the circumference of the bone. From a. 

 MS. Note b;i the Author. 



