136 MICROSCOPIC ANATOMY OF THE TEETH 



due to fracture, as has been suggested, for the course of the 

 tube is not altered, as one would expect to find if this were 

 the case. 



That this membrane completely closes the tube is shown 

 by the fact that small crystalline particles of the copper 

 salt accumulate upon its upper or proximal surface, the 

 lower part of the tube remaining clear. 



FIG. 79. Osmotic tube formed with copper sulphate in silicate of 

 potash. Osmotic membrane showing crystalline particles above and 

 calcospherites below. (x!5.) 



After some hours, however, spheroidal bodies appear in 

 the clear part of the tube below the membrane, many being 

 in close contact with it (fig. 79). These bodies have all the 

 appearances of calcospherites of the radial type. They are 

 probably composed of silicate of lime, the lime salts being 

 derived from the tap water in which the silicate is dissolved. 1 



1 These bodies below the membrane form also when distilled water is 

 used to dissolve the silicate, but, as Dr. Lovatt Evans says, this would 



