276 E. V. Cowdry, 



separation they assumed a more or less spherical shape. In some 

 cases the mitochondria were restricted to the zone of cytoplasm 

 immediately surrounding the nucleus, hut in other cases they extended 

 out into the pseudopod-like prolongations of the cytoplasm. 



These observations were controlled by the study of fixed and 

 stained preparations. The relations of mitochondria in disintegrating 

 lymphocytes were seen to best advantage in preparations fixed in 

 osmic acid and stained by the Altmann method. 



3. Lymphocytes (fig. 3 a, b and c). 



Synonyms: small mononuclear leucocytes. 



Mitochondria may be observed in the unstained condition without 

 any admixture of salt solution. 



Lymphocytes are more permeable to janus green than any other 

 blood cells. The mitochondria within them may be seen to take up 

 the dye under the microscope. They do so about 30 seconds after 

 the application of the stain, and before the mitochondria in any other 

 blood cells become colored. The nucleus remains unstained. In from 

 five to fifteen minutes the mitochondria attain a maximum coloration 

 with the janus green. Under favorable conditions a cell may be kept 

 in this condition for study for from one and half to two hours. The 

 nucleus then begins to take up the dye. At first the dye is merely 

 dissolved in the nuclear sap, but soon the chromatin stains and the 

 entire nucleus assumes a bright greenish blue color. This stage lasts 

 for a variable time depending upon the supply of oxygen from the 

 air, or more correctly on the rate of reduction of the dye in the 

 tissue. During this period the mitochondria remain unaltered. Their 

 outlines now become obscure, the shape of the cell somewhat irregular 

 with pseudopod-like prolongations, and the nucleus begins to show a 

 pink coloration which gradually deepens so that one obtains a beau- 

 tiful color contrast. This pink coloration is due to the liberation of 

 diethylsafranin. Fragments of the cytoplasm now break off from the 

 cell, the mitochondria disappear and the cell goes to pieces. 



The mitochondria may also be stained with diethylsafranin. The 

 sequence of changes is the same, as in the case of janus green, except 

 for the difference in color. 



