270 COLLOIDS IN BIOLOGY AND MEDICINE 



This investigator has simulated the formation and growth of the 

 long bones. He filled test tubes half full of gelatin which was made 

 alkaline, with tricalcium phosphate, for instance; this layer repre- 

 sented the periphery of the bone. After solidification there was 

 placed on top a thin coating of gelatin containing a suspension of tri- 

 calcium phosphate; this was to represent the bone. Upon this was 

 poured some acid solution, for instance, lactic acid; representing the 

 center of the bone. The acid diffuses through the tricalcium phos- 

 phate layer, dissolves the calcium, reaching the lower periphery, 

 where the calcium is precipitated again in layers as a phosphate. If 

 a suitable calcium salt is added with the lactic acid, the layer becomes 

 stronger and less porous; in a successful experiment, it shows, inside, 

 the characteristic worm-eaten appearance of the long bones, and out- 

 side, a smooth firm and sharply defined structure. As natural sources 

 of acids, R. LIESEGANG mentions the accumulation of C0 2 , lactic acid 

 and glycerophosphoric acid derived from lecithin. [BARILLE found 

 that tricalcium phosphate was dissolved by water containing C02 under 

 pressure, forming an unstable compound tribasic calcium carbon phos- 

 phate, Ca 3 P 2 8 + 4 H 2 C0 3 = H 2 O + P 2 8 Ca 2 : 2 CO (C0 3 H) CaJ 



In discussing calcification and ossification in his Harvey Lecture, 

 1910-11, H. GIDEON WELLS concludes that "there seems to be no 

 essential differences between the processes involved in normal ossifi- 

 cation and in most instances of pathological calcification. Any area 

 of calcification may be changed to true bone in the course of time/' 

 and that " calcium deposition seems to depend rather on physico- 

 chemical processes than on chemical reactions." JEROME ALEXANDER 

 suggests the importance of the removal of or alteration of protective 

 substances resulting in the deposition of calcium salts. Cf. also 

 HOFMEISTER'S observation on the difference between solubility of 

 calcium phosphate dissolved in serum and the dissolving of calcium 

 phosphate by serum. Tr.] 



Diseases of the Bone. 



Of the noninf ectious bone diseases, rickets and osteomalacia attract 

 our special attention. 



Rickets is characterized by lime-poor, so-called osteoid tissue, in- 

 stead of the solid calcareous structure. In this way a pliable mass 

 takes the place of the rigid framework. This lack of lime might 

 readily be attributed to a lack of lime in the food, but it has been 

 shown that this is certainly not the cause, since such a lack of lime 

 can be produced only by artificial preparation of the food. In my 

 opinion FAULT'S theory of bone formation offers a good explanation 

 for rickets. He supposes, as indicated on page 268, a preliminary 



