222 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The pedicles of the cilia, though in directum with the distal ends 

 of the intracellular fibres, are not mere enlargements of these fibres. 

 Engelmann expressly states that the relation between the fibres and 

 pedicles is one rather of contiguity than of continuity. Nor are the 

 pedicles simple prolongations of the cilia ; they are specialized parts, 

 having their own optical and chemical properties, differing both from 

 the fibres and the cilia proper. The pedicles rest upon the outer 

 portion of the protoplasm or are sunk just beneath its surface. They 

 lie close to each other, with intervening parallel streaks of soft cell- 

 substance, or they constitute by their lateral union a membrane- 

 like mosaic, also termed the operculum. The homology of this 

 operculum with the cuticular border of certain intestinal cells is 

 obvious. That we have here a true mosaic of bacilliform elements, a 

 genuine plinth to the cilia, and not a sieve through whose pores the 

 cilia pass (as wrongly stated by Eberth and by Mai'chi), is now shown 

 by the concurrent testimony of Eimer (1877) and Engelmann. In all 

 ciliated cells which possess these pedicles, their relation towards the 

 cilia seems the same. The pedicles exhibit single refraction, the 

 fibres and cilia double refraction. Eosin stains strongly alike the 

 fibres and cilia, but has less effect on the pedicles. Methyl-green also 

 stains equally, though weakly, the cilia and their fibres ; it acts much 

 more readily on the pedicles. Anilin-blue, indulin, carmine and 

 picrocarmine, especially the first, colour the cilia but faintly in com- 

 parison with the tinge which they impart to both the intracellular 

 fibres and pedicles. 



The intermediate segments, which very generally separate the 

 pedicles from their cilia, are easily seen in many fresh cells. If not 

 so, reagents can show that the threshold of the cilium differs from the 

 cilium proper. Each segment is usually less than • 5 /a, very seldom 

 2 fji long. Its refractive index scarcely exceeds that of water. In 

 such cells, careful profile views reveal between the pedicles and cilia 

 a clear (protoplasmic or secreted) border with very delicate parallel 

 striae. The segments do not display double refraction. They are 

 much softer and more destructible than either the cilia proper or the 

 pedicles. When cilia are cast off they usually give way so that one 

 portion of the segment clings to the cilium proper, another to the 

 pedicle ; but the whole of the segment may remain attached to 

 either. 



The bulb, often well seen in isolated cilia, refracts somewhat more 

 strongly than the shaft. When best displayed, it appears as a fusiform 

 or spherical thickening about • 5 /x long. From what has been said 

 it is plain that between the intracellular fibres and the shafts of the 

 cilia three layers may be distinguished. These are respectively con- 

 stituted by (1) the pedicles, (2) the intermediate segments, and 

 (3) the bulbi. Thus the first and third layers may be very clearly 

 separated by the much fainter intermediate layer. 



The shaft of the cilium is directly continuous with its bulb, like 

 which it shows double refraction. In no case could Engelmann dis- 

 tinguish a cuticular sheath with protoplasmic contents, as described 

 by Simroth. Frequently the apices of the shafts become regularly 



