MITOCHONDRIA AND BACTERIA 212 



MITOSIS 



Schridde's method (Ergn. Anat. u. 

 Entw., Bonnet, XX, 1911) can also be 

 recommended as giving beautiful prep- 

 arations of mitochondria. 



4. Pritchard's silver method (J. Anat., 

 1951 , 85, in press) . This method, which 

 is dependent upon reduction of silver 

 on the slide, gives very beautiful and 

 precise preparations of mitochondria 

 which show up black. Small pieces of 

 tissue should be fixed in Regaud's or 

 Helly's fluid for 3 da3's and post- 

 chromed for 4 days in 3% aq. potassium 

 bichromate. Prepare paraffin sections 

 in the usual way, avoiding excessive 

 heat in flattening and drying. Remove 

 paraffin and proceed to aq. dest. Slides 

 placed for 20 sec. with agitation into a 

 dilute solution of silver diamino hy- 

 droxide (Wilder's Solution diluted with 

 an equal volume of aq. dest. to which 

 is added 2 drops of 8% NH4OH per 50 

 cc). Drain quickly and without rins- 

 ing immerse in a large volume (e.g. 200 

 cc.) of very dilute formalin (1/1000 

 commercial formalin in aq. dest.) agi- 

 tating for 10-20 sec, not more. Fresh 

 formalin solution for each section is 

 preferable. Wash in aq. dest. Dif- 

 ferentiate carefully under the micro- 

 scope with 1-2% aq. potassium ferri- 

 cyanide until mitochondria show up 

 black against a clear background. 

 Wash in aq. dest., counterstain with 1% 

 Safranin or Ponceau fuchsin. Regaud's 

 fixative gives the best results but after 

 Helly's fluid the Golgi element is often 

 sharply impregnated as well as the mito- 

 chondria. 



Mitochondria and Bacteria. Demonstration 

 in the same cells. See Cowdry, E. V. 

 and Olitsky, P. K., J. Exper. Med., 

 1922, 36, 521-533, Cowdry, E. V., Am. J. 

 Anat., 1923, 31, 339-343. Stain as for 

 mitochondria with Anilin Fuchsin and 

 Methyl Green. Mitochondria are col- 

 ored crimson. When the bacilli are acid 

 fast as in leprosy they are colored a dark 

 reddish purple; but when they are not 

 acid resistant they are stained bluish 

 green. 



Mitogenic Radiations. It is questionable 

 whether these rays, said to generate 

 mitosis, really exist. A critical and 

 well balanced statement is afforded by 

 Glasser, O., in Glasser's Medical Phy- 

 sics, 760-763. 



Mitosis (G. Mitos, thread). Indirect nu- 

 clear division in which the chromatin 

 forms a thread which breaks up into 

 chromosomes. 



Material should be freshly fixed, less 

 than half hour after removal. But mito- 

 sis can be seen in some tissues 24 hrs. or 

 longer after death, especially if the body 

 is kept at a low temperature but the 



number is less and the details not so 

 clear as after quick fixation (Mallory, 

 p. 108). Sat. mercuric chloride in 70% 

 ale. plus 5% acetic acid, Zenker's fluid, 

 formalin-Zenker , Bouin's fluid and Flem- 

 ming's strong fluid are satisfactory 

 fixatives but the last named penetrates 

 very badly. 



The most beautiful stain for mitotic 

 figures is safranin light green but the 

 mitoses can be more clearly distin- 

 guished without the green counterstain. 

 Simply deparaffinise and stain sections 

 in anilin-safranin (Babes), wash quickly 

 in tap water, differentiate in acid alcohol 

 until the resting nuclei are less intensely 

 colored than the dividing ones, wash in 

 95%, dehydrate in abs. clear in xylol 

 and mount in balsam. 



Another excellent method is to apply 

 the Feulgen reaction for Thymonucleic 

 Acid to sections of tissues preferably 

 fixed in Carnoy's fluid or acetic subli- 

 mate. This demonstrates thymonucleic 

 acid in the chromatin, and the dividing 

 nuclei, as with safranin, are more deeply 

 stained than the others. This method 

 is displacing the older safranin tech- 

 nique. 



To demonstrate mitosis in whole 

 mounts of epidermis place freshly ex- 

 cised skin (circumcision specimen pre- 

 ferred) in 0.1% aq. acetic acid in the 

 icebox over night. Wash quickly in 

 aq. dest. Strip off the epidermis with 

 needles, stain it like a section with 

 anilin-safranin or with Harris' hema- 

 toxylin and mount with the outer sur- 

 face uppermost. This technique could 

 probably be adapted to relatively flat 

 epithelia of the respiratory digestive, 

 urinary and genital systems. 



In order to reveal the maximum num- 

 ber of mitotic figures it is important to 

 study the mitotic rhythm of the par- 

 ticular tissue or organ and take tissues 

 at the peak which in the case of the 

 human foreskin is probably between 

 9 p.m. and midnight (Cooper, Z. K. and 

 Schiff, A., Proc. Soc. Exp. Biol. & Med., 

 1938, 39, 323-324). The relation of 

 alimentation and nutrition to cyclic 

 variations in mitotic activity is pre- 

 sented by Blumenthal, H. T., Growth, 

 1950, 14, 231-250. 



To experimentally increase the num- 

 ber of mitosis use colchicine which ar- 

 rests the process chiefly in the meta- 

 phase by causing failure of the mitotic 

 spindle to form and function (Ludford, 

 R. J., Arch. f. exper. Zellf., 1936, 18, 

 411-441). Consequently as long as the 

 cells are under the influence of colchi- 

 cine — a matter of a few hours only — 

 mitosis begins as usual; but, since it is 

 not completed, the proportion of mitotic 



