Experimental Growth in Animals 237 



luimlxi can be ex]jlainecl on the basis of niitoiic arrest. i"- -"• -i Some 

 show only slight abnormalities, but most are of the exploded tvpe 

 (Fig. 2.5) . A\nien u|) to one-fifth of all the li\er cells are in this 

 condition, swollen and their chromosomes dispersed, the liver be- 

 comes extremely friable.-- The various stages of restitution after the 

 injection of colchicine have been descriljcd and illustrated in C>hapter 

 2. It is surprising that the regeneration is only slightly slowed down 

 by several injections of the sublethal dose of 50 mg. This has been 

 explained by the fact that the exploded metaphases, after building 

 cells ^vith many micronuclei, regained normal nuclei by the fusion 

 of the micronuclei (Figs. 2.7. 2.8, 2.9) . These facts remain rather 

 difficult to understand from a quantitati\e point of view. 



Apart from this work, liver regeneration studied \vith colciiicine 

 has pro\ided some material for counting the chromosomes. This is 

 done readih in the exploded metaphases. Diploid, tetraploid, and 

 octojjloitl nuclei were observed, a fact which agrees with karyometric 

 chita.'"' About the analysis of the differential growth of various liver 

 constituents — liver cells, Kupfter cells, bile canaliculi, blood vessels 

 — hardly anything is known, and there remain ample opportunities 

 for fin ther colchicine research.^-^- '''^- "^^ The biochemical stimulus to 

 mitotic growth after hepatectomy is also unknown; some unpub- 

 lished results obtained at Brussels indicate that the ligature of bile 

 ducts ma\ increase mitoses, as observed in the liver b\ the colchicine 

 method. 



p-y-::: Kidney. The increase of the \olimie of one kidney after 

 removal of the other is closely related to regeneration. It proceeds 

 by mitotic growth. This is particularly difhcult to analyze in such 

 a complex organ as the kichiey, and any tool increasing the niunber 

 of visible mitoses is most helpful.^'' ^'■^- -^^ The great ninnber of mitoses 

 obser\ed in rats injected with 2.5 mg/kg after tniilateral nephrectomy 

 and killed 10 hours later is apparent from Table 9.8. 



The jjroblems of kidney mitoses in this condition and in other 

 experiments carried on to throw light on the causal factors have 

 been the object of several jniblications from the Brussels school. After 

 tmihiteral nephrectomy, the maximal niunljer of mitoses is found 

 during the first four days in the convoliued tidjules, then in the 

 glomeruli, and on the seventh day in Henle's loops and the Schweig- 

 ger-Seidel tubules.^i- *'■'' No mitoses are to be foimd in the epithelium 

 of the renal }jelvis. Exploded c-mitoses are the most frequent in 

 the con^oluted tubes. If a partial nephrectomy is added to the abla- 

 tion of the other kidne), the remaining tissue shows mitoses in all 

 locations, including the pelvis. Ligation of the ureter, without ne- 

 phrectomy, also stimulates kidney cells to divide, a fact ^\hich may 

 prove of great experimental importance"'^ (Fig. 9.10). .Another re- 



