Collagen and Apatite in Hard Tissues and Pathological Formations 147 



by means of the above mentioned methods that they, too, were apatitic, although we 

 had first assumed them to be collagen subfibers without apatite. 



Concerning the thin, dark-looking, apatitic formations (Fig. 1, arrow 2) we con- 

 cluded that: 1. they are formed earlier than the above mentioned light-looking 

 crystallites, 2. they are in a more disordered stage of crystalllnity. We reached the 

 first conclusion from the fact that in the initial stages of collagen mineralization in 

 myositis ossificans, cementum, dentine or turkey leg tendon (Nylen et al., 1960) only 

 the thin, dark-looking formations could be seen. In the case of myositis ossificans we 

 observed (Themann and Hohling, 1964 — 1965), as Glimcher (1961) did in the 

 case of bone and collagen mineralization in vitro, first the so-called "dots" out of 

 which the very thin, dark, rodlike formations develop. 



s the light-looking ip i i 



ingi; ot 6301-.C \ 



lud in the pipei. M xgniiic 



We reached our second conclusion i.e. that they are not apatite crystallites with 

 a fully developed crystal-lattice, from several independant observations. Reimer 

 (1962, Fig. 1) found on electron microscopic examination of thin metal foils that they 

 looked darker in a more amorphous state and that they became lighter in appearance 

 when converted into a more crystalline state. The dark appearance of the thin 

 apatitic formations might therefore, result from poor crystallinity. Furthermore, the 

 fact that they show relatively few electron diffraction lines, that they are often bent, 

 that they are of unequal thickness throughout their whole length and that they are 

 very thin, might support the conclusion that they are still in an initial state of 

 crystallinity. 



10* 



