The mitotic apparatus is a structure of obvious biological and medical
interest, but it has proved to be a difficult cellular machine to
understand. The chemical composition of the spindle is only slightly
elucidated, largely because of the difficulties in preparing useful isolates
of the structure. Chemical studies of the mitotic spindle have been reviewed
elsewhere (Mcintosh, 1977), and will not be discussed further here. One
would think that structural studies on the mitotic apparatus (MA) in situ
would be straightforward, but even with this approach there is some
disagreement in the results obtained with various methods and by different
investigators. In this paper I will review briefly the approaches which have
been used in structural studies of the MA, pointing out the strengths and
problems of each approach. I will summarize the principal findings of the
different methods, and identify what seem to be fruitful avenues for further
work.