118 M. van Tieghem on the Amylaceous Globules 



form is spherical or ovoid ; sometimes they are flattened and dis- 

 coidal or lenticular in form, sometimes irregular. They are 

 formed by a very distinct colourless or rose-coloured membrane, 

 filled with solid greyish contents, most frequently without any 

 central space, but sometimes with a cavity in the centre, which 

 it is not unusual to see divided into several compartments. The 

 full globules are of two kinds : some, and by far the greater 

 number, have a circular outline and are simple ; their contents, 

 apparently homogeneous, are formed of very delicate concentric 

 zones, and give a very clear black cross in the polarizing ap- 

 paratus ; the others, variable in form and aspect, are composite, 

 and show a system of concentric layers and a black cross in each 

 of their compartments, when these are sufficiently large. 



The very variable dimensions of these globules is in relation 

 to their degree of development : the ordinary diameter of the 

 well-developed grains is from 0-013-0-015 millimetre; the 

 maximum observed was 0*025 milhmetre. Iodine gives them 

 a reddish-yellow colour. This tint persists upon all the globules 

 whatever be the quantity of tincture of iodine employed ; but 

 when we renew the liquid which bathes the grains in proportion 

 as it evaporates, replacing it alternately by a drop of tincture of 

 of iodine and a drop of water, at the edges of the covering glass, 

 where the osmotic movements produced by an alternate disic- 

 cation and humectation with liquids of difi'erent densities are 

 most active, we see the globules become altered in a remarkable 

 manner at the same time that their colour changes. Sometimes 

 there appears at the centre a small circular space, which enlarges 

 by degrees, the layers becoming dissolved successively from 

 the centre to the periphery, at the same time that the globule 

 enlarges and becomes discoidal; it is reduced at last to a 

 membrane, which becomes more and more delicate, entire or 

 irregularly torn, and as the granule becomes empty its tint 

 passes to pure violet. In other cases the solution commences 

 by a circle of small holes, which increase radially, remaining 

 separated by solid rays ; the centre is at the same time hollowed, 

 and the outer membrane, being unable to yield equally to the 

 inflation, becomes undulated; the globule is then of a fine 

 violet, and presents the aspect of a wheel, of which the nave, 

 the spokes, and the undulated felly are of a deep violet, and the 

 intervals of a lighter tint. In the composite globules, formed of 

 compartments arranged in a circle round a central chamber, 

 the contents of each compartment become dissolved by de- 

 grees, the granule swells, becomes of a fine violet colour, and 

 presents the radiated appearance which I have just described, 

 with still more distinctness. This disorganization of the gra- 

 nule with blue coloration may, however, be produced rapidly. 



