IX] ON SPHERULITES OR CALCOSPHERITES 425 



is in great part a physical phenomenon; the actual deposit in both tissues 

 occurs in the form of calcospherites, and the process in mammalian tissue 

 is identical in every point with the same process occiu-ring in lower organisms*." 

 The ossification of bone, we may be sure, is in the same sense and to the same 

 extent a physical phenomenon. 



The typical structure of a calcospherite is no other than that 

 of a pearl, nor does it differ essentially from that of the otolith 

 of a mollusc or of a bony fish. (The otohths, by the way, of the 

 elasmobranch fishes, like those of reptiles and birds, are not 

 developed after this fashion, but are true crystals of calc-spar.) 



Throughout these phenomena, the effect of surface-tension is 

 manifest. It is by surface-tension that ultra-microscopic particles 

 are brought together in the first floccular precipitate or coagulum ; 



f^ 



O 



Fig. 201. A '"crust" of close-packed 



calcareous concretions, precipitated -r-i- , —. . 11 



at the surface of an albuminous Fig. 202. Aggregated calco- 

 solution. (After Harting.) sphentes. (After Harting.) 



by the same agency, the coarser particles are in turn agglutinated 

 into visible lumps ; and the form of the calcospherites, whether 

 it be that of the solitary spheres or that assumed in various stages 

 of aggregation (e.g. Fig. 202) f, is likewise due to the same agency. 

 From the point of view of colloid chemistry the whole phe- 

 nomenon is very important and significant; and not the least 

 significant part is this tendency of the solidified deposits to assume 

 the form of " spherulites," and other rounded contours. In the 

 phraseology of that science, we are dealing with a ttvo-phase 

 system, which finally consists of sohd particles in suspension in 

 a liquid (the former being styled the dis'perse phase, the latter the 



* Mummery, J. H., On Calcification in Enamel and Dentine. Phil. Trans, ccv 

 (B), pp. 95-lli, 1914. 



t The artificial concretion represented in Fig. 202 is identical in appearance 

 with the concretions found in the kidney of Nautilus, as figured by Willey [Zoological 

 Results, p. Ixxvi, Fig. 2, 1902). 



