Experimental Growth in Animals 245 



at least three days. Such a fixation of the alkaloid in tissues has not 

 been described in j)]iarniacological work (Chapter 7) . The inhibition 

 ot regeneration Avas clearly the consequence of a great number of 

 the mitoses, sometimes up to 70 per cent, being destroyed after a 

 prolonged period of metaphase arrest (cf. Chapter 3) S'^ Similar re- 

 sults have been re]M)rted in Rtnia tempornria tadpoles. The local 



days 



Fig. 9.14 — Inhibition of the regeneration in the tail of Xenopus laevis after a short 

 treatment with colchicine. Dotted line: normal growth curve. I. Inhibition of regener- 

 ation for more than 5 days, then resumed growth. II, III. Strong and persistent inhi- 

 bition of growth. (After Lehmann et al. 1945, and Lijscher" ) 



application of a 1:500 M solution of colchicine for only 20 minutes 

 inhibits the regenerative growth of the tail, but has no influence on 

 the gro^\•th of the tadpole.^'' 



These facts, ajiart from the conclusion that colchicine is not 

 always a harmless "tool," indicate a remarkable property of the alka- 

 loid of becoming fixed in some tissues. This is surprising for a sub- 

 stance soluble both in water and in lipids. Pharmacologists should 

 pay attention to this possibility, for instance in the analysis of the 

 action of colchicine on muscle and brain. Nearly all data available 

 on colchicine metabolism in warm-blooded animals contradict this 



