DEVELOPMENT OF THE ENAMEL 135 



these physical processes take in the phenomena under con- 

 sideration. 



The author undertook some experiments with solutions 

 of lime salts in inorganic solutions, to ascertain, if possible, 

 to what extent the deposition of these bodies in the forms 

 found in calcifying tissues was produced by purely physical 

 agencies, and how far the phenomena of osmosis were con- 

 cerned in bringing this about. 



Professor Leduc's experiments on the production of 

 osmotic growths in chemical solutions suggested the examina- 

 tion of the production of similar growths under the micro- 

 scope. 



When a solution of silicate of potash in tap water (con- Osmotic 

 taining lime salts) was employed, into which a few particles juries 

 of copper sulphate were dropped, the phenomena were 

 easily followed under a low power of the microscope. When 

 the copper salt was dropped into the solution, the smaller 

 particles immediately gave rise to a number of small con- 

 voluted tubes, but in the larger pieces the process was less 

 rapid and more easily followed. A globular projection 

 appears at the margin of the little mass of crystals ; this is 

 still further protruded by a series of small explosive impulses, 

 and eventually the limiting membrane formed between the 

 dissolving crystalloid and the surrounding colloidal medium 

 is pushed forward in the form of a steadily growing tube. 

 These tubes can be watched as they lapidly pass across the 

 field of the microscope, some terminating in pointed ex- 

 tremities, others reaching the margin of the microscope 

 slide. The growth of these tubes is due to the rapid passing 

 of water through the membranous wall from the surround- 

 ing solution by osmosis, the distension caused by the water 

 pushing the tube forward, the resistance of the membrane 

 at the same time preventing the lateral bulging of the tube. 



These membranes were first described by Traube (27), Traube's 

 who called them ' membranes of precipitation '. The most ^nesoi 

 interesting point, however, to notice in this experiment is pretipita 

 that in many places, as the tube nears the end of its growth, 

 a line is seen to be drawn across it, dividing it with a distinct 

 septum. It is difficult to explain what determines the pro- 

 duction of these transverse membranes. It can hardly be 



