314 JAMES CRAWFORD WATT. 



Plate 2. 



Photomicrographs all taken at a standard magnification, X 200, with dark 

 field condenser in use. 



Fig. 25. Crystals of calcium carbonate precipitated by ammonium carbonate 

 in water. 



Fig. 26. Calcium carbonate precipitated by sodium carbonate in a solution 

 of egg albumen containing N/10 sodium chloride. 



Fig. 2j . Calcium carbonate precipitated by potassium carbonate in water 

 containing 0.1 per cent, lecithin. Note one double spherule and three large 

 single spherules of which the two larger show indications of the radial divi- 

 sions which will result in splitting the spherule into crystals of triangular out- 

 line. Many small crystals and spherules seen. 



Fig. 28. Calcium carbonate precipitated by ammonium carbonate in water 

 containing 0.1 per cent, lecithin. 



Fig. 29. Calcium carbonate precipitated by potassium carbonate in a solu- 

 tion of egg albumen containing 1 per cent, ethyl alcohol. 



Fig. 30. Calcium carbonate precipitated by potassium carbonate in a solu- 

 tion of egg albumen containing 0.05 per cent. urea. 



Fig. 31. Calcium carbonate precipitated by sodium carbonate in a 1 per 

 cent, solution of gelatin previously treated with 1/1024 HC1 solution. Clear 

 spherules, some seen from side appearing disc-like. 



Fig. 32. Calcium carbonate precipitated by sodium carbonate in a 1 per 

 cent, solution of gelatin previously treated with 1/2048 HC1 solution. Some 

 crystals are present. Spherules begin to show an opaque central dot, the first 

 indication of a coming disintegration. 



Fig. 33. Calcium carbonate precipitated by sodium carbonate in a 1 per 

 cent, solution of gelatin previously treated with 1/512 HC1 solution. This 

 field was formerly all spherules, now some crystals are seen. Spherules are 

 far advanced in disintegrative process, are completely opaque, and are dissolv- 

 ing, some appearing only as ghosts of their former selves. 



Fig. 34. Calcium carbonate precipitated by ammonium carbonate in 1 per 

 cent, gelatin solution containing 0.05 per cent. urea. Rings and striations seen 

 in spherules. 



Fig. 35. Calcium carbonate precipitated by sodium carbonate in a 1 per 

 cent, gelatin solution containing 0.05 per cent. urea. Field of very small 

 mixed crystals and spherules. 



Fig. 36. Combined precipitate of calcium phosphate and calcium carbonate 

 by action of sodium phosphate and sodium carbonate in dog's blood serum. 

 The calcium carbonate shows as seven spherules. The calcium phosphate 

 shows as a cloud of very fine amorphous granules, which is the form in which 

 it precipitated in all experiments. 



