MODIFICATIONS OF MITOSIS 



6 9 



that asymmetrical mitoses, exactly like those seen in carcinoma, may 

 be artificially produced in the epithelial cells of salamanders (Fig. 

 33) by treatment with dilute solutions of various drugs (antipyrin, 

 cocaine, quinine). 



Normal multipolar mitoses, though rare, sometimes occur, as in the 

 division of the pollen mother-cells and the endosperm-cells of flower- 

 ing plants (Strasburger); but such mitotic figures arise through the 

 union of two or more bipolar amphiasters in a syncytium and are 

 due to a rapid succession of the nuclear divisions unaccompanied by 

 fission of the cell-substance. These are not to be confounded with 

 pathological mitoses arising by premature or abnormal division of the 

 centrosome. If one centrosome divide, while the other does not, 

 triasters are produced, from which may arise three cells or a tri- 



A B 



Fig. 33. Pathological mitoses in epidermal cells of salamander caused by poisons. 

 [GALEOTTI.] 



A. Asymmetrical mitosis after treatment with 0.05% antipyrin solution. B. Tripolar mitosis 

 after treatment with 0.5% potassic iodide solution. 



nucleated cell. If both centrosomes divide tetrasters or polyasters 

 are formed. Here again the same result has been artificially attained 

 by chemical stimulus (cf. Schottlander, '88). Multipolar mkoses are 

 also common in regenerating tissues after irritative stimulus (Strobe); 

 but it is uncertain whether such mitoses lead to the formation of 

 normal tissue. 1 



The frequency of abnormal mitoses in pathological growths is a 

 most suggestive fact, but it is still wholly undetermined whether the 

 abnormal mode of cell-division is the cause of the disease or the 

 reverse. The latter seems- the more probable alternative, since normal 

 mitosis is certainly the rule in abnormal growths ; and Galeotti's 



1 The remarkable polyasters formed in 

 scribed at p. 147. 



polyspermic fertilization of the egg are de- 



