Techniques of Colchicine Treatment 38 J 



colchicine from acting on animal cells as in j)lants. I7nder the head- 

 ing of polyploidy should be considered only doubling or multiplying 

 by 2, 3, 4, . . . the numbers of chromosomes (cf. Chapter 11). Most 

 results obtained with colchicine are related to trijjloidy. 



Any experimental change in the numbers of chromosomes should 

 be checked by chromosome counts. This point may seem quite obvi- 

 ous, but in early reports of "polyploidy" in mammals, changes in 

 cell volume alone were mentioned. It is known from previous experi- 

 mental data, mainly on amphibians,-' that the size of the polyploid 

 animals remains the same, or is even smaller, than the diploid size, 

 though individual cells become larger and larger with increasing 

 numbers of chromosomes. However, to deduce from measurement of 

 cell size alone the degree of -ploidy cannot be accepted as a valid 

 scientific method.'"' Considerable error may be involved; for instance, 

 making smears of red blood cells and comparing the diameters is 

 incorrect and cannot bring evidence of triploidy, as has been 

 claimed. •'^2' ^^ The red blood cell volumes would be a better choice, 

 but these were not measured, either by indirect calculation from the 

 diameter, or by measuring the packed red blood cell volume in a 

 hematocrit tube. Some "polyploid" mammals have been claimed to 

 be larger and to grow faster than the euploid ones.^^-' •''•"' This is in 

 contradiction with all data on amphibia, and as the numbers of 

 colchicine-polyploid animals which have been studied is very small, 

 and as they were not of pure breed, the data lack the necessary 

 statistical significance.*'' 



In the work on the unicelhdar Amoeba sphneronucle'iis, poly- 

 ploidy was assessed without counting the chromosomes, which are 

 very numerous and small. Here, the action of the alkaloid injected 

 intracellularly at metaphase could be followed under the microscope. 

 A single nucleus resulted from the arrested metaphase, and its volume 

 was roughly double that of normal amoebae. Checks were made 

 possible by grafting these abnormal nuclei into normal amoebae, and 

 vice versa. ^^ The cellular voliune became proportional to the size 

 of the nucleus. However, even in these experiments, mitotic abnormal- 

 ities were observed in the "polyploid" species, and it is not possible 

 to assert with certainty that a true doubling of the chromosome num- 

 ber and not aneuploidy had resulted from the injections of colchi- 

 cine. Claims of colchicine-induced polyploidy in frogs, rabbits, and 

 pigs have been repeatedly published. ""^2' ^^' ^^ The females were artifi- 

 cially fertilized by sperm mixed with colchicine. The alkaloid is sup- 

 posed to reach the e^g at the time of the second maturation division, 

 which ^voidd be arrested. The egg woidd thus remain dij:)loid, and 

 after fertilization with haploid sperm, triploid animals would be 

 expected. Monstrous development in frogs treated similarly had pre- 



