1879.] Influence of Colloids upon Crystalline Form, Sfc. 239 



ether passes off, the cholesterin is deposited in the substance and on 

 the surface of the albumen. The superficial deposit is partly crys- 

 talline, but the deposit in the albumen is entirely spherical or acicular. 

 The crystals on the surface are rarely perfect, and generally have rounded 

 angles (Plate 1, figs. 1, 2). The spheres are of all sizes up to inch 

 diameter, and are at first homogeneous and singularly lustrous (fig. 17). 

 But they speedily begin to undergo internal disintegration. Becoming 

 cloudy, they are soon made out to be composed of fine short needles, 

 packed together like very closely cropped hair, brushed in a direction 

 running from one pole to the opposite (figs. 3 — 11). Subsequently 

 they break up into tufts of hair-like needles, radiating in a brush from 

 the pole of divergence, and these tufts expand and grow till each 

 of them becomes a long curl or ringlet of wavy hair (figs. 10, 11). 

 By the end of a week nearly all the cholesterin has come to this state 

 of long curling fibrils, and the whole process may remind the observer 

 of the growth of minute confervoid filaments from spores. 



A new series of phenomena is observed when the albumen, having 

 the cholesterin immersed in it, is treated with glacial acetic acid. 

 But before describing this change, the behaviour of cholesterin in 

 presence of acids may be described. 



Experiment 2. — Treated with nitric acid cholesterin loses its crystal- 

 line form with some effervescence, and swells out irregularly at its 

 surface, throwing off oily-looking spherules. Finally it is entirely 

 resolved into such spherules. 



Experiment 3. — Treated with hydrochloric acid it undergoes little or 

 no change. 



Experiment 4. — On the addition of glacial acetic acid to pure choles- 

 terin, the rhombs are seen under the microscope to undergo an instant 

 change of structure. They break up internally into crystalline fibres, 

 usually springing from one of the angles ; and they emit radiating 

 tufts of sharp-pointed needles which seem to grow at the expense of 

 the substance of crystals. If, now, the slide be heated till the acid 

 begins to boil, the cholesterin is wholly or in part dissolved ; but, as 

 the slide cools, acicular crystals shoot out from any portion of choles- 

 terin that is left undissolved, or from new centres, and rapidly cover 

 the field. These crystals during their growth give the impression of 

 their being protruded like spears. They are often as thick as the 

 spicules of fresh water sponge, and as refractile. They are solid. The 

 cholesterin appears in this case to be chemically altered by the acetic 

 acid, combining with it to form a sort of ether. 



Experiment 5. — Some pure glycerin being added to such a prepara- 

 tion as is produced in the preceding experiment, during cooling, at any 

 point where the glycerin meets the growing spears it breaks them up 

 wholly or partially into globules, making them look as if they had 

 been put into the fire and fused. 



