29O JAMES CRAWFORD WATT. 



calcium carbonate. Even in aqueous solution (Figs. 4, 5, 6) 

 Spherules occur in great numbers, and many of these are of a large 

 size not obtainable in other solutions. There is also a distinct 

 tendency toward fusion of spherules in contact with each other, so 

 that double and multiple forms are numerous. Beautiful rosettes 

 (Fig. 5) were present, due to the adhesion of many oval-shaped 

 bodies. 



In gelatin and albumen (Figs. 10 and 11) the same phenomena 

 occurred, producing magnificent rosettes and very large spherules 

 measuring 120 /* in diameter. 



Lecithin thus has a very typical colloidal action on the precipitate, 

 favoring the spherical forms of deposit. This compound is found 

 in blood in seven times the strength it was employed here, and is 

 also found in bone and other tissues, so that its action on a pre- 

 cipitation of bone salts, if such occurs, ought to be appreciable. 

 This point will be discussed later. 



Addition of Acetone. 



The presence of acetone (Fig. 12) hastens the process of pre- 

 cipitation, making it occur very rapidly, and also makes the initial 

 deposit at the moment of contact much denser and more complete. 

 This point is rather suggestive. It leads to the question as to 

 whether or not conditions of acidosis such as accompany serious 

 cases of nephritis and diabetes have an influence favoring the prog- 

 ress of calcification in the arteriosclerosis so often found in these 

 cases. 



Addition of Ethyl Alcohol. 



The alcohol had no appreciable effect upon precipitation except 

 to add to the optical clearness of some preparations. 



The Influence of Different Ions. 

 The calcium carbonate was precipitated in separate cells by the 

 carbonates of sodium (Figs. 1 and 4), potassium (Figs. 2 and 5), 

 and ammonium (Figs. 3 and 6), so that the solutions contained the 

 three last-named ions as the only variable, all other factors being 

 equal. In aqueous solution the crystal form of the calcium car- 

 bonate in the three cases was noticeably different. In colloidal 



