RAINEYj ON CARBONATE OP LIME GLOBULES, 33 



Borne further Experiments and Observations on the Mode 

 of Formation and Coalescence of Carbonate of Lime 

 Globules^ and the Development of Shell-tissues. By 

 G. Rainey, M.R.C.S., Lecturer and Demonstrator of 

 Microscopical and Surgical Anatomy at St. Thomas's 

 Hospital. 



As I believe it is generally admitted, especially by those 

 who have examined my specimens of carbonate of lime, as it 

 occurs in shell-tissues, and compared them with the analogous 

 artificial forms, that both are formed in the same manner ; 

 and as in this case the experimental investigation of the arti- 

 ficial process will furnish the best clue to a precise and certain 

 knowledge of the natural one, by showing more clearly how 

 much is due to physical agency, I have been anxious to ex- 

 tend and improve my former process for obtaining the globular 

 form of carbonate of lime by making the conditions more 

 like the natural ones, and by so performing the experiments 

 that the changes, which the carbonate undergoes in its pas- 

 sage from an apparently amorphous state to large globules, 

 may, as they are taking place, allow of being examined by the 

 microscope. 



The process about to be described is the same in principle 

 as that given in the " Transactions of the Microscopical So- 

 ciety,'^ published in the ' Quarterly Journal of Microscopic 

 Science' for January, 1858. It consists in employing a very 

 shallow cell, open at both ends, for the decomposition of the 

 salts of lime contained in gum-arabic by subcarbonate of 

 potash. This cell is made by cementing two ledges of thin 

 glass, about two inches in length and a quarter of an inch in 

 width, placed parallel with one another, to a microscope-slide, 

 and placing upon them a thin glass cover, fixed in its place 

 by thick gold-size. At one of the ends of this cell a very 

 thick and clear solution of gum-arabic is to be introduced by 

 capillar}'' attraction, sutficient in quantity almost to fill it, and 

 at the other a small quantity of still denser solution of gum, 

 saturated with subcarbonate of potash, sufficient, with the first 

 solution, entirely to fill the cell. The alkaline solution should 

 be sufficient to fill about a fifth of it. The excess of gum is 

 then to be removed from each end, after which they are 

 to be closed up by very thick gold-size, or some similar 

 cement. The cell thus charged should be kept in a horizontal 

 position, and examined by the microscope as occasion may 

 require. The rapidity with which the globules will be formed. 



