INTRODUCTION 



Centrifugation techniques have become a cytological tool by- 

 means of which various celkilar components have been separated, 

 and the isolated constituents have been subjected to chemical study 

 in certain instances. The value of this procedure is twofold. The 

 point of view stressed by Bensley ( 1942) that "to separate separable 

 things before proceeding to their analysis" requires no elaboration 

 or defense. In addition, sufficient material can be isolated in many 

 cases to permit chemical investigations on a relatively macro scale, 

 thus obviating the need for special, and often less available, tech- 

 niques. Cytochemical work on the separated formed bodies is really 

 just beginning, and a large proportion of the work still must be 

 directed toward perfecting the separations themselves. 



As Danielli (1946a) has warned, the centrifugal segregation of 

 particulates from cells could possibly alter the enzyme activities 

 associated with the particulates m situ. This may or may not be 

 a factor in specific instances, but in the interpretation of data it 

 should be kept in mind. 



The centrifuge microscope, cleverly designed by E. N. Harvey 

 and A. L. Loomis, has enabled direct observation of cells at high 

 magnifications while they are being spun in a centrifuge. In this way 

 it has been possible to determine the manner in which some cellular 

 components become segregated under centrifugal force and to 

 observe the actual scission of certain cells. The instrument and its 

 application, not only to separations, but also to the determination 

 of particular physical characteristics, such as surface forces, have 

 been described by Harvey (1932, 1933). 



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