376 Colchicine 



In mammals, and especially the small rodents, which have been 

 widely used for colchicine work, some tissues are most favorable for 

 the study of mitosis and the influence of colchicine and similar poi- 

 sons. The skin lends itself to repeated biopsies, for instance the ear 

 of the mouse, from which small fragments may be punched out at 

 hourly intervals.i-^- " However, the mitotic activity of the skin is low, 

 and counting is long and tedious, even after colchicine. The num- 

 ber of mitoses is increased little by mitotic arrest, probably because 

 under normal conditions they are of long duration, up to three hours. 

 The influence of the sexual cycle is considerable (Chapter 9, Fig. 9.6) 

 and must not be overlooked. i" The cornea may be studied by stain- 

 ing whole mounts and counting the number of mitoses per thousand 

 cells; this method has only been utilized in mammals by one group 

 of workers,is though it appears to offer many advantages over the 

 skin. Bone marrow and intestinal crypts are zones of maximal mitotic 

 growth in mammals. They both provide excellent material for study- 

 ing the action of colchicine. In bone marrow, comparative studies 

 may be made between the white-cell- and the red-cell-forming tissues. 

 In the intestine, quantitative estimation of mitotic growth is possible,^^ 

 though the counting of mitoses may be difficult because of their rapid 

 destruction of pycnosis. The intestinal mitoses have been one of the 

 best tools for the study of mitotic poisons at Brussels. Contrary to 

 the mitoses of lymphoid tissue, which are strongly affected by hor- 

 monal influences such as those of the "alarm-reaction" or pituitary- 

 adrenal stimulation,^! the intestine provides a tissue with uniform 

 growth,"*'^ not affected by the adrenal cortical hormones.-^ Intestinal 

 fragments should always be taken from the same location, for the 

 mitotic activity is greater in the duodenum, and decreases gradually 

 towards the large intestine, where few mitoses are seen. The gastric 

 mucosa of the mouse has also been proposed;**' ^^ it offers an interest- 

 icing comparison between squamous-celled and glandular epithehum 

 in a single organ. The regenerating liver is a favorable material in 

 rats, and quantitative estimations of mitotic growth are possible. ^^ 

 However, it has been shown that the repartition of mitoses was not 

 uniform throughout the remaining liver.^^ 



Local applications of colchicine have been most useful in the study 

 of c-mitosis and regeneration in amphibians." The study of recovery 

 after a prolonged colchicine impregnation (five days) has been dis- 

 cussed in Chapter 2 (cf. Fig. 2.7) .^^ The inhibition of regeneration 

 of the tail of Xenopus larvae has been illustrated in Chapter 9; the 

 technique involved a local application of an aqueous solution of 

 colchicine to the amputated tail.44 Local apjjlication has also been 

 found useful in studies on the mitotic activity of genital tissues in 

 rodents-^s and of the human vagina before removal of a fragment by 



