VII.] MITOSIS OR KARYOK1NESIS. 



LESSON VII. 



STRUCTURE OF CELLS MITOSIS OR KARYO- 

 KINESIS. 



Structure of the Animal Cell. To see all the structures in an 

 animal cell is by no means easy. Speaking generally, the tissues 

 of the articulata, amphibians, and reptiles yield the largest tissue 

 elements for examination. The cells may be examined in the fresh 

 condition or after "fixing," hardening, and staining. 



In Fresh Condition. Examine a teased preparation in an 

 indifferent fluid, e.g., normal saline, the liquid of Ripart and Petit 

 (p. 24), or in solution of methyl-green (p. 74). The preparation may 

 be sealed up with paraffin wax (p. in) and examined after some 

 time. 



After Hardening. The best osmic acid "fixing" fluids for this 

 purpose are the fluids of Flemming, Rabl, and Fol, and the best 

 stains safranin and gentian-violet. Mount in xylol-balsam. 



To see the finer details an oil-immersion lens and Abbe's con- 

 denser must be used. 



Mitosis or Karyokinesis. By these terms is meant the remark- 

 able series of phenomena which take place in cells animal and 

 vegetable when they undergo a process of indirect division. In 

 this connection it is important to remember the constitution ' of a 

 cell and some of the terms which have been applied by different 

 authors to its several parts. A cell may or may not possess a dis- 

 tinct cell- wall, but the cell-body appears to be made up of two 

 substances, which Flemming names as follows : One composed of 

 threads, seldom forming a network, and called by him cyto-mitoma 

 or mitoma (/xtVos, thread), also called spongioplasm, and the 

 other, homogeneous and lying in the meshes of the latter, is the 

 paramitoma or hyaloplasm. The cell-contents are generally 

 described as consisting of a finely-granular soft substance, the so- 

 called pr<>tt>i>1<i#m (fig. 105). This protoplasm consists of a network, 

 sometimes called a "filar mass" or spongioplasm, which lies em- 

 bedded in a homogeneous ground-substance or "interfilar maw " or 

 hyaloplasm. The filar oaass corresponds to the mitomaot Flemming 

 and t<> the Bponfjioplasm of some other authors, while the interfilar 

 mass corresponds to the p<traniito)na, or the hyoiofAasn^ or para- 

 of some authors. 



