HOW MOLECULES MAKE MASSES 51 



tinal* movements, belonging so far to the same class of conditions as 

 the spheroidal state of water. . . . 



"The idea of a 'combination' between the colloid and the crystalloid 

 as constituting an essential part of the whole phenomenon is insisted 

 upon by both Mr. Rainey and Professor Hartung. If by this is meant 

 chemical combination, the idea does not seem to be to be well founded. 

 The observation of Professor Hartung that albumen undergoes a chem- 

 ical change where the spheres are formed — an observation which 

 agrees with what occurs in urinary calculi — does indeed go to show 

 that a chemical interaction goes on between the two substances. This 

 might be expected to occur when they have been so intimately 

 commingled. But the fact that variations in the density of the colloid 

 solutions produce the phenomena of molecular disintegration alone 

 shows the union to be of physical and not of chemical nature; the 

 history of long-formed spheres, of urinary and of cholesterin calculi in 

 particular, shows that in process of time there is an actual mechanical 

 separation of the colloid from the crystalloid within the substance of 

 the spheres, without loss of the spherical form, so far as it is possessed 

 by the whole mass. . . .f The quantity also of colloid present in a 

 sphere is extremely small in proportion to the crystalloid . . . Such a 

 fact, it is true, is not decisive, but it is at least opposed to the ordinary 

 laws of combination between colloids and crystalloids, a small pro- 

 portion of the latter usually combining with a large proportion of the 

 former. And, if a combination takes place, why is it limited only to 

 an area of the colloid collimitary with the area of the densely-packed 

 saline matter?" 



Dr. Ord then suggests that the relative compactness of bone in dif- 

 ferent classes of vertebrates depends upon three factors: (a) the nature 

 of the colloid matrix; (b) the nature of the earthy salts; (c) the tem- 

 perature of the body. Greatest compaction is obtained with albu- 

 minous matrix, with a mixture of calcium carbonate and phosphate, 

 and with the highest temperature, as in birds. He adds that bone 

 "may be excavated by a process of molecular disintegration set going 

 by a variation in the constitution of the colloid matrix." (This sug- 

 gests that enzymic attack on bone collagen might be involved in 

 osteomalacia and pregnancy.) 



My own early experiments (1907) speedily showed that the na- 

 ture of the form developed by any salt depends greatly upon the 

 kind of colloid admixed with its solution, and that with the same 

 colloid different salts give different forms. Thus a solution of 

 one part of sodium chloride, one part of sodium carbonate, and 



* This word means "of or belonging to the inner parts." J. A. 

 f See paper on concretions by Dr. L. Lichtwitz, in Alexander's "Colloid Chem- 

 istry," Vol. V, Reinhold Publishing Corp., 1944. 



