574 POPULAR SCIENCE MONTHLY. 



nucleus contained in it. On the contractile theory, the radiations 

 which form the body of the spindle, either by actual traction of the 

 supposed fibrillse or by their pressure on the nucleus which they sur- 

 round, might impel during karyokinesis the dividing chromosome ele- 

 ments toward the poles of the spindle, to form there the daughter 

 nuclei. On the dynamical theory, the chemical and physical energy 

 in the centrosome might influence the cell plasm and the nucleus 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 applied 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 substance which partly lined the cell 

 wall (primordial utricle) and partly traversed the interior of the cell as 

 delicate threads inclosing spaces (vacuoles) in which the cell juice was 

 contained. In the protoplasm the nucleus was embedded. Nageli, 

 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 bladder or vesicle could no longer 

 be sustained in the animal tissues, the name 'cell' continued to be re- 

 tained for descriptive purposes, and the body of the cell was spoken of 

 as a more or less soft substance inclosing a nucleus (Leydig). In 1861 

 Max Schultze adopted for the substance forming the body of the ani- 

 mal cell the term 'protoplasm.' He defined a cell to be a particle of 

 protoplasm in the substance of which a nucleus was situated. He re- 

 garded the protoplasm, as indeed had previously been pointed out by 

 the botanist Unger, as essentially the same as the contractile sarcode 

 which constitutes the body and pseudopodia of the Amoeba and other 

 Ehizopoda. 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 homogeneous, 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 func- 

 tion of the nucleus could not be defined. Based upon this conception 



