434 ON CONCRETIONS, SPICULES, ETC. [ch. 



body of an organism soon introduce us to a multitude of kindred 

 phenomena, of which our knowledge is still scanty, and which we 

 must not attempt to discuss at greater length. As regards our 

 main point, namely the formation of spicules and other elementary 

 skeletal forms, we have seen that certain of them may be safely 

 ascribed to simple precipitation or crystalhsation of inorganic 

 materials, in ways more or less modified by the presence of 

 albuminous or other colloid substances. The effect of these 

 latter is found to be much greater in the case of some crystallisable 

 bodies than in others. For instance, Harting, and Rainey also, 

 found as a rule that calcium oxalate was much less affected by 

 a colloid medium than was calcium carbonate; it shewed in 

 their hands no tendency to form rounded concretions or "calco- 

 spherites" in presence of a colloid, but continued to crystalhse, 

 either normally, or with a tendency to form needles or raphides. 

 It is doubtless for this reason that, as we have seen, crystals of 

 calcium oxalate are so common in the tissues of plants, while 

 those of other calcium salts are rare. But true calcospherites, 

 or spherocrystals, of the oxalate are occasionally found, for 

 instance in certain Cacti, and Biitschli* has succeeded in making 

 them artificially in Harting's usual way, that is to say by crystal- 

 lisation in a colloid medium. 



There link on to these latter observations, and to the statement 

 already quoted that calcareous deposits are associated with the 

 dead products rather than with the living cells of the organism, 

 certain very interesting facts in regard to the solubility of salts 

 in colloid media, which have been made known to us of late, and 

 which go far to account for the presence (apart from the form) 

 of calcareous precipitates mthin the organism f. It has been 

 shewn, in the first place, that the presence of albumin has a notable 

 effect on the solubility in a watery solution of calcium salts, 

 increasing the solubility of the phosphate in a marked degree, 

 and that of the carbonate in still greater proportion ; but the 



* Spharocrystalle von Kalkoxalat bei Kakteen, Ber. d. d. Bot. Gesellsch. 

 p. 178, 1885. 



f Pauli, W. u. Samec, M., Ueber Loslichkeitsbeeinfliissung von Elektrolyten 

 durch Eiweisskorper, Biochem. Zeitschr. xvii, p. 235, 1910. Some of these results 

 were known much earUer; cf. Fokker in Pfluger's Archiv, vn, p. 274, 1873; also 

 Irvine and Sims Woodhead, op. cit. p. 347. 



