IX] HARTING'S MORPHOLOGIE SYNTHETIQUE 421 



Rainey and Harting used similar methods, and these were 

 such as many other workers have continued to employ, — partly 

 with the direct object of explaining the genesis of organic forms 

 and partly as an integral part of what is now known as Colloid 

 Chemistry. The whole gist of the method was to bring some soluble 

 salt of lime, such as the chloride or nitrate, into solution within a 

 colloid medium, such as gum, gelatine or albumin ; and then to 

 precipitate it out in the form of some insoluble compound, such 

 as the carbonate or oxalate. Harting found that, when he added 

 a little sodium or potassium carbonate to a concentrated solution 

 of calcium chloride in albumin, he got at first a gelatinous mass, 

 or "colloid precipitate": which slowly transformed by the 



Fig. 195. Calcospherites, or concretions 

 of calcium carbonate, deposited in 

 white of egg. (After Harting.) 



Fig. 196. A single calco- 

 spherite, witli central 

 "nucleus," and striated, 

 iridescent border. (After 

 Harting.) 



appearance of tiny microscopic particles, at first motionless, but 

 afterwards as they grew larger shewing the typical Brownian 

 movement. So far, very much the same phenomena were wit- 

 nessed whether the solution were albuminous or not, and similar 

 appearances indeed had been witnessed and recorded by Gustav 

 Rose, so far back as 1837 * ; but in the later stages the presence 

 of albuminoid matter made a great difference. Now, after a few 

 days, the calcium carbonate was seen to be deposited in the form 

 of large rounded concretions, with a more or less distinct central 

 nucleus, and with a surrounding structure at once radiate and 

 * Cf. Quincke, Ueber unsichtbare Fliissigkeitsscliichten, Amt. der Physilc, 1902. 



