236 



V. CAGLIOTI, A. ASCENZI AND A. SANTORO 









Fig. 2. Pseudo-replica of bone, etched with a 1 "o HNO3 

 solution. 



Fig. 3 a and b. Pseudo-replicas of bone digested with trypsin, 

 in b, a thin fragment of bone stripped oti" the replicated 

 surface. 



which ossein has been removed (see fig. 1) follows 

 the Wiener law on the mixed rod-shaped body (1,7, 

 16). According to Schmidt who made special obser- 

 vations in this connection, such an optical behaviour 

 is due to the penetration of fluids at diff"erent refrac- 

 tion indices in the ultramicroscopical holes already 

 occupied by the micellae of osteomucoid and osteoal- 

 buminoid. 



{b) A bone system resulting from inorganic parti- 

 cles or crystallites dispersed in the ossein, according 

 to Engstrom and Finean, could not subsist when 

 ossein had been removed, as the particles would 

 break down into an "incoherent" powder. On the 

 contrary, bone from which ossein has been removed, 

 subsists as a coherent structure though its resistance 

 is greatly decreased. In addition, the polarizing 

 microscope and the low- and wide-angle x-ray dif- 

 fraction patterns demonstrate that the structural 

 orientation of the inorganic fraction is unmodified. 

 Finally the curve of form birefringence can be 

 recorded from the bone without ossein (see above). 



(f) It is very important to note that the change 

 observed in the low-angle scatter of the bone from 

 which ossein has been removed according to Ga- 

 briel's method appears as new evidence of the neces- 

 sity to interpret the low-angle scatter of the bone as 

 organic ellipsoidal particles enclosed in the holes 

 circumscribed by the inorganic fraction. Indeed such 

 a change is neither related to the orientation nor the 

 physical state of the inorganic crystallites, both con- 

 ditions being unmodified by Gabriel's treatment, 

 according to the wide-angle x-ray diffraction pat- 

 terns. Therefore it is more plausible to maintain that 

 in the homogeneous body pertaining to the inorganic 

 bone fraction the removal of the organic substance 

 from the hole results in an arrangement of the 



material delimiting the same holes. This view finds 

 ready support in the existence of the chemical bonds 

 between ossein and the inorganic bone fraction (5). 



(d) Our studies in progress suggest that in foetal 

 bone the low-angle scattered radiation shows inter- 

 ference patterns. This finding can be interpreted as 

 the result of the higher concentration of the scatter- 

 ing elements. It may be assumed therefore that 

 organic elements are responsible for the x-ray 

 scatter, as they are less dispersed in foetal bone in 

 consequence to lower content of calcium salts. 



This array of arguments is supported by the pres- 

 ent electron microscopical investigations. The re- 

 sults shown in figs. 2 and 3 give the most outstanding 

 findings. In fig. 2, corresponding to the pseudo- 

 replica prepared from bone previously etched with a 

 1 °o HNO., solution, the ground substance is made 

 up of small globules or particles apparently spherical 

 in shape. The same globules are often arranged end 

 to end, building up a network of regularly aligned 

 fibrils. Pseudo-replicas obtained from bone di- 

 gested with trypsin (fig. 3o) show a very fine frame- 

 work, the meshes of which delimit spaces correspond- 

 ing in size to globules which have been removed, 

 belonging to the ground substance. Fig. 3/? shows 

 a thin fragment of digested bone removed from the 

 sample in stripping the pseudo-replica. The struc- 

 ture appears as a very fine framework delimiting 

 round spaces. The maximum diameter ranges from 

 200 to 250 A. 



According to the electron microscope investiga- 

 tions of Barbour (4) the diameter of the holes per- 

 taining to the inorganic bone fraction ranges from 

 a minimum of 62 A to a maximum of 225 A. 



The inorganic bone fraction may be regarded as a 

 homogeneous body with holes occupied by the 



