428 GERMINAL ORGANIZATION INDUCTION PHENOMENA 4 



otocysts and truncal structures^ (Kawakami and Mifune, 1955); mouse liver, inducing an 

 acrencephalon (Kawakami and Mifune, 1955); various organs of irradiated mice, which 

 show a more acrogenic tendency (Kawakami and Mifune, 1957); bone marrow and kidney 

 medulla of mice injected with nitrogen-mustard-JV-Oxide, which induce less mesoblast and more 

 neural structures, with a shift towards acrencephalic organs (Mifune, 1957); and finally 

 crude extract of 9-days chicken embryos, inducing mostly deutencephalic structures, acces- 

 sorily truncal ones (Von Woellwarth, 1956). 



These instances suffice to authenticate the existence in vivo of these inducing 

 properties and their wide distribution as well as their variability, even concerning 

 one kind of implant. In the case of the mouse kidney, the discrepancies are due 

 to the exact origin of the tissue, the outer layer of the cortex having an acren- 

 cephalic effect, while the inner layer of the cortex and the medulla provoke 

 notogenesis (Mifune, 1955). In spite of these variations, probably due to the 

 complexitv and physiological state of the organs used, the distinction emerges 

 between the two familiar types of induction, with a hint that another more 

 limited category exists: that of isolated lenses, evidently related to the acren- 

 cephalon. 



{b) Killed foreign tissues 



The same two groups of results appear, but more consistent, when we consider 

 the effects of the same organs used after boiling or dipping in ethanol, as done 

 by Holtfreter ( 1 934b) , Chuang ( 1 939, 1 940) , Toivonen ( 1 940) and Rotmann ( 1 942) . 

 A change, however, is produced by these treatments, whereby most inductions 

 take on an acrencephalic character. Chuang had the merit of recognizing that 

 boiling the mouse kidney for increasing periods up to one hour causes progressive 

 increase of the inductive ability which becomes mostly acrogenic; with longer 

 boiling, up to 2 h., this property gradually fades and practically disappears. 

 Newt liver also loses its notogenic effect by boiling, after only a few minutes. 

 With 5 min. or more boiling it exerts a stronger acrogenic action, which dis- 

 appears after 15 min. treatment. 



In his extensive investigations of 1940, Toivonen always used as implants 

 specimens treated with ethanol. He obtained acrencephalic structures when 

 implanting either liver pieces of perch, or viper, guinea pig, and snake kidney, 

 while kidney pieces of perch, shrike and guinea pig were consistently notogenic. 

 Guinea pig thymus was found to induce lenses, while Rotmann (1942) observed 

 only tail formation; this odd discrepancy turned out to depend on the age of 

 the donor and also on the length of the ethanol action. Englander, Johnen and 

 Vahs (1953) indeed established that this factor causes a shifting from notogenesis 

 to acrogenesis in the cases of guinea pig kidney, parotis, heart, and thymus 

 (Fig. 83, A, B). They also showed that food deficiency {cf. also Toivonen, 1951) 

 works in the same way, but the frequency of rhombencephalic structures is not 

 appreciably modified (Fig. 83, C), a feature also noticed with alcoholization of 

 the parotis (see also Englander and Johnen, 1957). 



Among inductions obtained with other heated and ethanol-treated organs are 



^ According to Mifune (1955), this effect is only obtained when using the inner part of 

 the renal cortex and the medulla ; the superficial part of the cortex is more acrogenic. 



