1879.] Influence of Colloids upon Crystalline Form, §c. 241 



This series of observations has, in the first place, some importance 

 as involving a rapid mode of exhibiting the influence of colloids upon 

 crystalline form. In Mr. Rainey's original processes, and in the later 

 experiments made by Harting, of Utrecht, and by myself, the forma- 

 tion of spherules of crystalline matter within colloids has been effected 

 only on a microscopic scale, and in the most gradual way. And 

 although Professor Gruthrie has recently, in independent and original 

 experiments, obtained large spherical masses of sulphate of copper by 

 the slow evaporation of solutions of that substance mixed with gelatin, 

 it has not been possible to watch so continuously the steps of the pro- 

 cess. But here, within a short compass, we are able to see the crys- 

 talloid cholesterin assume, when first deposited within the substance of 

 the colloid, perfectly spherical form ; we can follow the gradual eman- 

 cipation of the crystalloid from the control of the colloid and its 

 return to a quasi- crystalline form within the albumen, and to definite 

 crystals within the gelatin or glycerin with acetic acid. We may infer 

 that the crystalloid is not so intensely crystalloid in its tendencies 

 when first deposited as afterwards. We may infer also that the power 

 of the colloid is, under certain circumstances, when coagulation is not 

 produced, intensified by heat ; and, in the loss of controlling power 

 experienced by the cooling colloid, we may see a parallel to the loss of 

 power experienced by a degenerating colloid, for instance in the tran- 

 sition from mucous to horny matter. Where the changes are most 

 rapid, as in the heated mixture of cholesterin, acetic acid and glycerin, 

 the transformation is seen to be accompanied by vigorous in- 

 testine movements. To review this observation, we have before us 

 in such a mixtrre, when cooling has only just commenced, perfect 

 lustrous spheres looking like drops of oil. Of a sudden these are 

 affected by peristaltic movements, and, as the surface contracts, the 

 mass is resolved into minute spheres. The heat and the crystallinity 

 have balanced each other for a time, but when the balance has been 

 lost and the process of crystallisation has commenced, the first step 

 has been not the formation of crystals, but of smaller spheres. So 

 long as all was quiet, the large sphere was possible ; but when mole- 

 cular vibrations were set up as the attendants of crystallising separa- 

 tion, the molecules at opposite ends of poles were withdrawn from 

 their power of holding one another in position at such a distance, and 

 the general shaking allowed only of the existence of small spheres, 

 the constituent particles of which were all near enough to each other 

 to allow of each exercising strong enough attractive influence on its 

 fellow to resist the distracting influence of the vibrations set going by 

 the crystallising force. Instead, therefore, of one centre around which, 

 or through which, all attractions were balanced, we have a number of 

 centres with spheres drawn round them proportionate in minuteness 

 to the activity of the perturbing force. The process, in one aspect, 



