Septejibee 7, 1900.] 



SCIENCE. 



367 



the spindle, to form there the daughter 

 nuclei. On the dynamical theory, the chem- 

 ical and physical energy in the centrosome 

 might influence the cell plasm and the nu- 

 cleus, and attract the chromosome elements 

 of the nucleus to the poles of the spindle. 

 The radiated appearance would therefore be 

 consequent and attendant on the physico- 

 chemical activity of the centrosome. One 

 or other of these theories may also be ap- 

 plied to the interpretation of the significance 

 of the polar radiations. 



CELL PLASM. 



In the cells of plants, in addition to the 

 cell wall, the cell body and the cell juice 

 require to be examined. The material of 

 the cell body, or the cell contents, was 

 named by von Mohl (1846) protoplasm, 

 and consisted of a colorless tenacious sub- 

 stance which partly lined the cell wall 

 (primordial utricle), and partly traversed 

 the interior of the cell as delicate threads 

 enclosing spaces (vacuoles) in which the 

 cell juice was contained. In the proto- 

 plasm the nucleus was embedded. NageU, 

 about the same time, had also recognized 

 the difference between the protoplasm and 

 the other contents of vegetable cells, and 

 had noticed its nitrogenous composition. 



Though the analogy with a closed blad- 

 der or vesicle could no longer be sustained 

 in the animal tissues, the name ' cell ' con- 

 tinued to be retained for descriptive pur- 

 poses, and the body of the cell was spoken 

 of as a more or less soft substance enclosing 

 a nucleus (Leydig) . In 1861 Max Schultze 

 adopted for the substance forming the body 

 of the animal cell the term 'protoplasm.' 

 He defined a cell to be a particle of proto- 

 plasm in the substance of which a nucleus 

 was situated. He regarded the protoplasm, 

 as indeed had previously beeen pointed out 

 by the botanist Unger, as essentially the 

 same as the contractile sarcode which con- 

 stitutes the body and pseudopodia of the 



Amoeba and other Rhizopoda. As the term 

 ' protoplasm,' as well as that of ' bioplasm,' 

 employed by Lionel Beale in a somewhat 

 similar though not precisely identical sense, 

 involves certain theoretical views of the 

 origin and function of the body of the cell, 

 it would be better to apply to it the more 

 purely descriptive term ' cytoplasm ' or 

 ' cell plasm. ' 



Schultze defined protoplasm as a homo- 

 geneous, glassy, tenacious material, of a 

 jelly-like or somewhat firmer consistency, 

 in which numerous minute granules were 

 embedded. He regarded it as the part of 

 the cell especially endowed with vital 

 energy, whilst the exact function of the 

 nucleus could not be defined. Based upon 

 this conception of the jelly-like character of 

 protoplasm, the idea for a time prevailed 

 that a structureless, dimly granular jelly 

 or slime destitute of organization, possessed 

 great physiological activity, and was the 

 medium through which the phenomena of 

 life were displayed. 



More accurate conceptions of the nature 

 of the cell plasm soon began to be enter- 

 tained. Briicke recognized that the body 

 of the cell was not simple, but had a com- 

 plex organization. Flemming observed that 

 the cell plasm contained extremely delicate 

 threads, which frequently formed a net- 

 work, the interspaces of which were occu- 

 pied by a more homogeneous substance. 

 Where the threads crossed each other, 

 granular particles (mikrosomen) were situ- 

 ated. Biitschli considered that he could 

 recognize in the cell plasm a honeycomb- 

 like appearance, as if it consisted of exces- 

 sively minute chambers in which a homo- 

 geneous more or less fluid material was 

 contained. The polar and spindle-like 

 radiations visible during the process of 

 karyokinesis, which have already been re- 

 ferred to, and the presence of the centro- 

 some, possibly even during the resting stage 

 of the cell, furnished additional illustra- 



