292 JAMES CRAWFORD WATT. 



a finely divided state, showed some tendency to form crystals, but 

 mostly was in form of granules and very small spherules. There 

 were no large spherules whatever. The total amount of deposit 

 would lead one to think that very weak solutions had been em- 

 ployed instead of the usual ones. 



Hyaline cartilage' extract thus seems to decrease the amount of 

 precipitation and to retain what deposit is formed in a very finely 

 divided state. Addition of the various accessory substances used 

 in previous cases had no effect, even lecithin apparently being 

 powerless to produce the large spherules. 



These facts may have some significance, for here we have an 

 extract of a tissue which although apparently similar to other carti- 

 lage which- does ossify, and although situated in continuity with 

 ossified tissue, yet retains a matrix free from a deposit Of calcium 

 salts. Its extract forms the most unfavorable medium yet found 

 in which to produce precipitation of calcium salts. Solutions of 

 equal concentration in other media give three to four times the 

 amount of precipitate found here. The experimental facts, it 

 seems, are in complete accord with the nature of the tissue, which 

 is unfavorable to the deposition of calcium salts in it. 



Influence of Hydrogen-Ion Concentration. 



Loeb's method was employed of treating gelatin to obtain it 

 with a definite hydrogen-ion concentration. To 0.25 gm. gelatin 

 in a test tube were added 20 c.c. of cold acid solution of a definite 

 strength, and this was allowed to stand for 30 minutes, during 

 which time the gelatin swelled remarkably, but did not dissolve. 

 It was then filtered and washed on the filter paper four times with 

 25 c.c. of cold distilled water at 5 C. to remove all free acid. 



The gelatin was then transferred to a test tube standing in hot 

 water, where it melted, and the volume was made up to 25 c.c. 

 with hot distilled water, thus giving a one per cent, gelatin solution. 

 Two tubes for each strength of acid were prepared. On cooling 

 the pH of each pair was determined approximately by Clark's 

 colorimetric method, and then one tube of the pair was rendered a 

 M/10 calcium chloride solution, and the other one a M/4 sodium 

 carbonate solution, and these two solutions were placed as usual in 

 a cell to react. 



