Experimental Growth in Animals 241 



the other kidney also; tliis resembles closely the changes of com- 

 pensator\ hypertrophy (Fig. 9.12) . Substances reabsorbed from the 

 mine ma\ promote division first in the ligated kidney and later 

 in the other one. Research by other workers has suggested that 

 xanthopterin or substances ol that chemical constitution may initiate 

 the kidnex hypertroi:)hy. The problems are far from being solved, 

 but the utility of colchicine for the observation of mitotic growth 

 has been amply demonstrated. 



9-^-^: Other organs. The folloAving results give an indication 

 of the multiple uses of colchicine as a tool. In the l.angerhans' islets 

 of the j:)ancreas, alloxan brings about a selectixe destruction of the 

 so-called |5-cells, which secrete insulin. Regeneration and mitoses of 

 these cells are j^revented if the animals receive insidin. This proba- 

 bly acts through a pituitary mechanism, for extracts of the pituitary 

 gland increase considerably the number of cell divisions in islet re- 

 generation. Colchicine-mitoses are also observed in the anterior lobe 

 of the pituitary-^''" (Table 9.10) . The regeneration of the adrenal 

 cortex after unilateral adrenalectomy in rats has also benefited from 

 the use of mitosis arrest. ^^ In rats also, colchicine helped to demon- 

 strate that compensatory hypertrophy of parathyroids after partial 

 parathyroidectomy does not take place in hyj:)ophysectomi/ed ani- 

 mals-"' and that testosterone inhibited the epithelial mitoses in thymic 

 regeneration following X-irradiation.-"' 



TABLE 9.9 



Action of Thyroxin on Renal Hypertrophy After Unilateral Nephrectomy: 

 Number of Mitoses in a Median Section of the Whole Kidney, 

 9 Hours After Colchicine 



(Abridged from Herlant^') 



* Animals weighing 260-360 gm. 



t Six daily doses of 0.25 mg. thyroxin; killed the seventh day after 2 mg/kg col- 

 chicine. Animals weighing 120-220 gm. 



