220 



Colchicine 



and the estrus cycle were carefully analyzed (Fig. 9.3) . In the endo- 

 thelial cells oi the theca interna of the ovarian follicles, immediately 

 before ovulation, the karyokineses were found to increase about sixty- 

 fold. Arrested mitoses of follicular cells in the rat can be found 

 around eggs after they have reached the uterus (Fig. 9.4) ^ Some 

 follicles are found to be growing rapidly while others are quiescent. 



I40 

 I30 

 I20 



no 



lOO 



90 



80 



12 70 

 I/) 



g 60 



u. 50 



O 



d 40 



z 



30 



20 



lO 



O 



16 



MITOTIC PROLIFERATION IN THE DEVELOPING AND 

 RETROGRESSING CORPUS LUTEUM 



endothelium 

 luteal cells 

 connective tissue 

 theca externa 



6 7 6 9 lO II 12 13 14 15 16 

 DAY OF ESTROUS CYCLE 



Fig. 9.3— Mitoses in the corpus luteum of the ovary of a normal mature guinea pig, 

 studied by the colchicine method. (After Schmidt") 



This fact is not evident in central animals, because the number of 

 mitoses is too small. 



In the pituitary glands of mice, colchicine increases the number 

 of mitoses about threefold. This is an indication that these mitoses 

 are normally of long duration. Many data have been gathered about 

 the mitotic activity in this organ in various physiological conditions. 

 '•• 5- Table 9.2 shows how evident is the action of age on mitotic 

 activity when the number of metaphases has been artificially in- 

 creased by spindle poisoning. ^'- 



A quantitative study of cell regeneration in the mucosa of the 

 intestine in rats has been made possible by colchicine. It was known 

 that the intestinal cells are continuously shed, but how long it took 

 for the whole epithelial lining to be replaced was not known. Table 



