THE BEGINNINGS OF LIFE. 6 1 



cles assume the form of calculi, with distinct con- 

 centric layers. These experiments have already been 

 alluded to '^ and I will now only add a few additional 

 particulars, which have a most important bearing upon 

 our present subject. Mr. Rainey says: — ^The mechani- 

 cal conditions required to act in conjunction with the 

 chemical means are, the presence of such a quantity of 

 the viscid material in each solution as will be sufficient 

 to make the two solutions, when mixed together, of 

 about the same density as that of the nascent carbonate 

 of lime, and a state of perfect rest of the fluid in which 

 the decomposition is going onj so that the newly-formed 

 compound may be interfered with as little as possible in 

 its subsidence to the sides and bottom of the vessel. 

 This will require two or three weeks or longer, accord- 

 ing to the size and completeness of the calculi 2/ The 

 early forms assumed by this globular carbonate of lime^ 



^ See vol. i. pp. 302-304. 



^ Just as the process of crystallization can be induced when it would 

 not otherwise occur, by the influence of electricity, so Mr. Bridgman, of 

 Norwich, has ascertained that under its influence the formation of 

 these calculi may be materially hastened. By availing himself of the 

 influence of a weak galvanic current he has succeeded ' not only 

 in producing them in a very much shorter period of time, but also 

 in obtaining a memfiranous matrix out of albumen, having within it 

 these deposits in a definite layer, coalescing and aggregating together, 

 and closely approaching the appearance presented at the edge of a 

 natural bone in its early stage of formation.' ('Transact, of Odont. 

 Soc' vol. iii. p. 410.) 



^ Mr. Rainey found that ' muriate of baryta and muriate of strontia 

 when treated in the same manner as the muriate of lime, furnish each a 

 globular carbonate, the spherical form of the latter being particularly 



