Chapter VI 



THE ACTION OF CYTOST 

 ON SINGLE CELLS 



Some years ago Leo Loeb (1897) observed that 

 excised somatic cells and tissues could be grown in 

 test tubes upon solid media such as blood agar, a 

 method which presented a serious drawback in that 

 the processes of growth and differentiation could not 

 be continuously observed. This difficulty was sur- 

 mounted by Harrison ( 1907) , who found that isolated 

 bits of nervous tissue taken from frog embryos could 

 be kept alive for many days in a hanging drop of frog 

 lymph. Such a technique permits the observation of 

 the cells by means of a high power microscope, and 

 present day methods of tissue culture are an elabora- 

 tion of Harrison's method. 



In general the technique is quite simple. Under 

 aseptic conditions tissues are excised from an animal 

 and immediately placed in a balanced salt medium, 

 such as Ringer's or Locke's solution. While so im- 

 mersed, the tissue is cut into pieces a millimeter square, 

 or less. These are then transferred to a sterile cover 

 slip, covered with a drop of suitable medium, and the 

 cover slip is then inverted over a depression in a sterile 

 slide and sealed in position. 



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