CALCIUM PHOSPHATE AND CALCIUM CARBONATE. 295 



loidal character, which I have shown is the natural condition with 

 the hydrogen-ion concentration on the basic side of the neutral 

 point. To the acid side of this point reactions tend to the ordinary- 

 chemical crystalline variety. 



Disintegration of Spherules. 



A most remarkable phenomenon was observed during the last 

 two months in some of the slides, where spherules have been ob- 

 served in process of disintegration and transformation into crystals. 

 This was first noticed in the acid gelatin series in a slide where the 

 gelatin had a pH of 4.9 and where for the whole of six months 

 appearance had been constant. 



This case (Fig. 31) had offered one of the most perfect exam- 

 ples of large spherules, which were of perfect outline, glassy trans- 

 parency, absolutely clear, and showing no indication at all of their 

 internal structure. These spherules were formed in half an hour 

 and had attained their full growth in less than two days, and for 

 six months presented the same appearance, with no indications of 

 a change. It happened at the end of this period that they were 

 not examined for about one month, when it was discovered that 

 some of them (Figs. 19 and 33) had disappeared, others were dis- 

 integrating, and all still present were opaque, while in this area 

 which had not previously shown a single crystal there was now a 

 number of large crystals. 



Other slides were examined for similar conditions without avail, 

 but a month later several of them showed signs of a change, and 

 by examination of these at intervals a complete series of stages in 

 the transformation has been obtained and a complete description 

 of it can now be given. 



The first sign of a change is in the occurrence of a very fine 

 opaque central spot of a bluish tint (Figs. 20, 21, 24a, and 32) in 

 the otherwise clear spherule. This area increases a little in extent, 

 and the next stage then is ushered in by the appearance around this 

 center (Fig. 246) of a faint nebulous haze, which becomes more 

 opaque and finally seems to consist of a fine radial striation (Fig. 

 24c) which extends farther and farther, until it reaches the pe- 

 riphery of the spherule, which is now an entirely opaque white 



