VII.] 



MITOSIS OR KARYOKINESIS. 145 



Some prefer to stain the sections,- e.</., after hardening in picric 

 acid -with Kleinenberg's logwood diluted with the alcoholic 

 solution of alum and calcium chloride (p. 68), allowing the sections 

 to stain for 12 hours or longer. They are mounted in balsam. 



N.B. It is important to note that tissues must be treated 

 differently according as one wishes to see the chromatic fibres or the 

 achromatic spindle. To see the ordinary mitotic figures, osmic acid, 

 or any fluid containing it, is good (12-24 hours) ; but in order to see 

 the achromatic spindle, it is better to use a chromo-acetic mixture 

 (p. 31) for 12 hours. 



ADDITIONAL EXERCISES. 



Mitosis, however, can also be studied in mammalian tissues. 



3. Mitosis in Omentum of New-Born Rabbit. Orth recommends the 

 omentum of a new-born rabbit. Harden it for twenty-four hours in Flem- 

 ming's fluid (p. 25) ; wash it thoroughly, and stain it in safranin-0 ; wash in 

 water, and remove the surplus dye, if necessary, by means of alcohol acidu- 

 lated with hydrochloric acid (p. 144). In the cells of the milk-spots and in the 

 walls of the blood-vessels it is easy to detect mitotic figures, but they are much 

 smaller than in the salamander. 



4. Mitosis in the Amnion. One of the readiest sources is the amnion of a 

 pregnant rat, as recommended by Solger. After the rat is killed, the uterus 

 is excised ;md placed in a saturated watery solution of picric acid. The uterus 

 and the membranes round each fcetus are opened under the picric fluid. 

 Harden for twenty-four hours ; wash well in water, and harden in the various 

 strengths of alcohol, beginning with 70 per cent. Better results are, I think, 

 obtained by removing tlie picric acid by washing in alcohol instead of water. 

 Select the amniotic membrane and tinge a small part of it in Ehrlich's acid 

 hsematoxylin (p. 69) diluted one-half. The membrane may ako be hardened 

 in Flemming's fluid and stained with safranin. 



5. Method of Martimotti and Resegotti. Small pieces of the tissue, e.g., a 

 rapidly growing tumour, are hardened in absolute alcohol. Sections are made 

 and coloured in a watery solution of safranin-0. The decolorisation, how- 

 ever, is obtained by a hydro-alcoholic solution of chromic acid. Take one to 

 two parts of a I per cent, solution of chromic acid to eight or nine of alcohol. 

 After it is sufficiently decolorised i.e., the colour is removed from every part 

 except the fibrils of the nuclei wash the section in absolute alcohol, clarify 

 in oil of bergamot, and mount in balsam. This method yields excellent 

 results. 



6. Mitosis in Plants. Various plants have been recommended, but my own 

 experience is limited to the following : 



(a. ) Take the fruit of Fritillaria iinperialis when they are 30-40 mm. in 

 length, and place them in absolute alcohol for a week. Then in equal parts 

 of glycerine find absolute alcohol for 24 hours. Then cut the fruit in two ; 

 with a dissecting microscope search for the embryo-sac. It shows various 

 stages of mitosis after staining for 12-24 hours in safranin. Mount in xylol- 

 balsaro. 



(b.) A transverse section of the fruit of Liliumcandulum also does very well. 

 14 K 



