238 Dr. W. Ord. Experiments on the [June 19, 



XXV. " An Account of Experiments on the Influence of Colloids 

 upon Crystalline Form, and on Movements observed in 

 Mixtures of Colloids with Crystalloids." By William M. 

 Ord, M.D. Lond., F.L.S. Communicated by J. Simon, 

 C.B., D.C.L., F.R.S. Received June 4, 1879. 



[Plate 1.] 



In the " Proceedings of the Royal Society " for 1866, Dr. Mont- 

 gomery has recorded some very remarkable observations -made by him 

 on the behaviour of " myelin " when brought into contact with water. 

 " Myelin " being a term of various applications, it is necessary to state 

 that the substance indicated in Dr. Montgomery's statement is an 

 alcoholic extract of yolk of egg. A small quantity being placed on 

 a microscope-slide, and covered with thin glass, is brought under 

 observation by a tolerably high object-glass. The mass is shapeless, 

 and indistinguishable from crushed grease till the addition of water, 

 when a multitude of minute rounded processes begin to sprout from 

 all parts of the surfacs exposed to the action of the water. The pro- 

 cesses are, when fairly formed, tube-like, with bulbous or simply 

 rounded ends, have a thick, retractile contour, and apparently fluid 

 contents. They remind one of nerve-tubes, or, still more closely, of 

 the tubular and rounded projections which are seen, under the micro- 

 scope, to issue from the cut ends of nerves in contact with water. 

 Dr. Montgomery shows in the same paper that, if albuminous fluid be 

 used instead of water, spheroidal protrusions are formed, and float free. 



Recently, in the examination of a biliary calculus containing much 

 cholesterin, my attention has been drawn to some very remarkable 

 changes of form undergone by that substance under certain condi- 

 tions — changes so important in their resemblance to phenomena 

 taking place in minute living organisms, that I am induced to give 

 an account of them. It will be seen that they belong partly to the 

 class of changes described by Dr. Montgomery, as above quoted, and 

 partly to those described by Mr. Rainey in his weU-known work on 

 "Molecular Coalescence." 



Pure cholesterin crystallises, as everybody knows, in the form of 

 colourless rhombic plates. It is insoluble in water and most saline 

 solutions, but is supposed to be held in solution in the bile by tauro- 

 cholic acid or the soda salt of that acid. In biliary calculi it is found 

 for the most part crystalline ; but at the surface of calculi and in 

 biliary gravel it often occurs in lustrous spherules. 



'Experiment 1. — An ethereal solution of cholesterin is added to fresh 

 egg-albumen in the proportion of one part to two. After good shaking 

 in a test-tube, the mixture becomes gelatinous, and is left for twenty- 

 four hours in the test-tube, or for any period exceeding half an hour, 

 in an evaporating dish to allow of free escape of the ether. As the 



