BINUCLEATE CELLS IN TISSUE CULTURES. 99 



The entire absence of division of the cell protoplasm prevents this nuclear 

 change from being regarded as a method of cell proliferation. Again, there is no 

 evidence that such nuclear fragments ever reunite to form a spireme after the manner 

 already described for the ordinary type of amitotic nucleus; indeed, mitotic figures 

 are absent from such preparations — a fact which seems to indicate that the condi- 

 tions which bring about fragmentation also prevent karyokinesis. 



The differences which fragmentation presents as compared with the usual form 

 of direct nuclear division may be briefly summarized as follows : The nucleus is of 

 irregular contour, multilobulated, and breaks up into a number of small, unequal- 

 sized parts, which frequently do not contain nucleoli; the nuclear parts remain 

 small, indicating that they have little or no power of growth, for the total volume 

 of the nuclear substance does not seem to be increased following division. There is 

 no evidence of fusion of the fragments contained in a single mass of cytoplasm to 

 form a single mitotic figure. Finally, the process is found in growths which are 

 existing under abnormal conditions, such as the presence of toxins or a deficiencj' 

 of oxygen, and such conditions act to prevent mitosis. 



As contrasted with this we find, in the case of the ordinary binucleate or multi- 

 nucleate cell, nuclear portions of regular contour, few in number (usually not more 

 than two), of almost equal size, each containing as a rule one or more nucleoli. 

 These parts apparently possess the power of growth, for in size they are comparable 

 with the nuclei of the mononucleate cell. The fragments of the "double" nucleus 

 are also able to combine and form a single mitotic figure. These cells are found in 

 normal cultures, in which mitotic figures are frequently to be seen. 



Fragmentation is similar to the division which produces the ordinary binucleate 

 cell in that the position of the centrosphere and mitochondria with relation to the 

 nucleus is the same. In figures 48 to 58 these structures will be seen occupying the 

 cleft, as in 55 and 58, or situated between the fragments, as in 50 and 54. 



Nuclear forms of this character are not infrequently found in the literature. 

 Glaser (1907) describes an analogous form of nuclear fragmentation which occurs in 

 the degenerating food ova of Fasciolaria tulipa. This he regards as "pathological 

 amitosis" as distinguished from physiological amitosis. Child (1907c, p. 288) 

 speaks of "degenerative amitosis" in starving planarians, stating that these forms 

 " differ in appearance from the amitoses in regenerating tissues;" again (1907e, p. 173) 

 he finds that "nuclear fragmentation is a frequent accompaniment of degeneration." 



On the whole, therefore, judging from the prevailing views of authors, and from 

 the conditions obtaining in the cultures in which it occurs, it seems reasonable to 

 regard nuclear fragmentation as an evidence of degeneration. These final changes 

 are, perhaps, to be looked upon as an active reaction of the nucleus to unfavorable 

 conditions of its environment, as, for instance, the presence of toxins due to katab- 

 olism, or chemical change in the media, or injurious material added to the media, 

 as alcohol, or to deficiency in food or oxygen. 



In this connection it is interesting to note that Lewis (1911) and Miller and 

 Reed (1912) demonstrated that the presence of toxins caused an increase in the 

 number of lobes of the neutrophilic leucocyte in blood of the human subject and also 

 in that of the guinea pig and rabbit. They look(>d upon this increase as a physio- 

 logical reaction on the part of the leucocj'te. AVherry (1913) found that amoebae 



