Techniques of Colchicine Treatment 375 



effective colchicine concentration, may not be of paramount impor- 

 tance. Tlie same may apply to some work where colchicine is mainly 

 a tool for increasing the "visibility" of cellular division. ^VHien the 

 topography of mitotic gro^^■th is the main purpose, several instances 

 of which have been given in Chapter 9, precise data about the mitotic 

 rate may not be important. On the contrary, when using colchicine 

 to assess the importance of cellular proliferation, either in complex 

 tissues or in tissue cultures, it is indispensable to understand the 

 complex action on the mitotic count. This point will be considered 

 further. 



Special techniques for the production by colchicine of abnormal 

 gi'owth in embryos have been mentioned in Chapter 8. The experi- 

 mental creation of polyploid animals has been one aim of colchicine 

 research. The methods used and the results obtained merit some dis- 

 cussion, which Avill be found in the last paragraph of this chapter. 



i6A.^-i: In vivo studies. Many methods have been utilized in the 

 study of c-mitosis in animal cells; they are all variants of two: viz., 

 placing cells in contact ^vith colchicine solutions, or injecting these by 

 various routes into the cell or into the animal. 



The intracellular injection is of great interest, for it was possible 

 to demonstrate by this procedure that some cells were resistant to 

 colchicine since the alkaloid did not penetrate into the cytoplasm. 

 Such experiments have been performed only on one unicellular. 

 Amoeba sphaeroiiiiclens. Mitotic division of this species is not affected 

 when it is grown in colchicine solutions. \'ery minute quantities of 

 a one per cent solution of the akaloid were introduced in the cyto- 

 plasm with a micropipette. Typical mitotic arrest, together with for- 

 mation of polyploid nuclei, restilted when the timing of the injection 

 was properly related to the mitotic cycle.-- 



Many cold-blooded animals, invertebrates, fish, amphibians, have 

 been studied after immersion in colchicine solutions. One important 

 pathway of absorption is through the branchiae. In such experiments, 

 care should be taken to avoid svmlight and to replace the colchicine 

 solution which may lose its activity through chemical changes. 



Injection is often the easiest way to administer colchicine to pluri- 

 cellular animals. In the study of hematopoiesis in the chick, colchi- 

 cine was simply injected into the egg yolk through the shell. ^ In 

 adtdt animals, subcutaneous or intraperitoneal injections are theniost 

 frequently used. One most important point, if a quantitative study 

 of the number of mitoses is needed, is to inject all animals at the 

 same hour of the day, so as not to be disturbed by the diurnal varia- 

 tions of mitotic rate.^-'' This is also influenced by feeding the animals, 

 more precisely by the blood glucose level, and experimental animals 

 should be kept under standard and specified dietetic conditions. ^^ 



