Techniques of Colchicine Treatment 379 



hundred glandular crypts. This method has been widely used by the 

 junior author in studies of mitotic poisoning.-^ 



Many data obscuring the problem of possible mitotic stimulation 

 by colchicine result from the difficulty of comparing tissues before 

 and after the action of the alkaloid. To cite one instance, the great 

 increase in mitotic activity in the crop-sac of pigeons injected with 

 prolactine and colchicine has l)een mentioned (Chapter 9) . Is it 

 possible to compare quantitati\ely the mitotic counts in this tissue? 

 From the figures which ha\'e been published one may conclude that 

 it is not, for after prolactine and colchicine, there is not the same 

 number of cells in a given area of tissue as in the same area of normal 

 epithelium or of prolactine-thickened crop-sac.^*' A quantitative re- 

 sult could only be correct if it were possible to count a very large 

 number of cells, and not only the mitoses in a given area. Such 

 counts are not often reported in this type of work (Chapter 9) . 

 Another error is that of injecting a hormone at a too short interval 

 before colchicine. Theoretically, the mitotic index should remain 

 constant; that is to sav, the niunbers of cells entering prophase should 

 not vary during the period of action of colchicine. It has been 

 pointed out that this is not often so with hormone-stimulated 

 growth. 1^' 23 Considerable errors may result from hasty interpretations 

 of the significance of mitotic increases. 



Any quantitative work supposes also that the exact number of 

 cells arrested at metaphase by colchicine is known. In warm-blooded 

 animals, and apparently also in amphibia,^' this is never so, even 

 with large doses. Increasing the dosage of alkaloid is never a good 

 solution either, for it increases secondary, nonspecific toxic reactions 

 and the percentage of destroyed arrested mitoses, and may also depress 

 the number of prophases. It is often very difficult, especially in mam- 

 mals, to know exactly how many metaphases with clumped chromo- 

 somes undergo degeneration, for this is rapid, and the nucleus breaks 

 down to many small fragments. The data about the duration of 

 c-mitosis in animals are scarce and widely divergent, as pointed out 

 in Chapter 2.^^ It is also necessary, when planning an experiment 

 with colchicine acting as a tool, to know how long after an injection 

 of the alkaloid the animal should be killed. Many factors complicate 

 this estimation: There may be a period of latency like that observed 

 in tissue cultures (Fig. 9.1) ;^- some anaphases may persist even with 

 large doses. Recovery starts after an interval which is not always 

 known. In some tissues this may be rather short, and in the study of 

 epidermal mitosis it is recommended to kill the animals six hours 

 after colchicine. This duration appears favorable for many experi- 

 ments on mammals, but it is obviously too short in cold-blooded 



