BATE OK REJUVENATION OF THE SKELETON 



195 



Table 4. Extent of Rejuvenation of the Skeleton of 

 A Rabbit in thk CoriiBE of 50 Days 



Fmclioii 



% rrcjuvenutcd 



Femur epij)hysis inorganic P 



Femnr epiphysis phosphatide P . . . . 

 Femur epiphysis glycerol extracl* P . . 



Femur diaphysis inorganic P 



Femur diaphxsis phosphatide P . . . . 

 Femur diaphysis glycerol extract* P 



Tibia epiphysis inorganic P 



TiV)ia diaphysis inorganic P 



Costa 



Scapula 



Incisor dentine, apical 



Incisor dentine, medial 



Incisor dentine, incisal 



Incisor enamel, apical -f- medial . . . . 

 Incisor enamel, incisal 



29.7 

 10(1 



.Jl.O 

 ().7 

 100 



H4:.r, 

 28.6 



7.0 

 27.5 

 43.8 

 103 

 !»S..-) 

 41.2 

 .S2.0 



(i.6 



* This fraction presumably contains some mineral P. 



he same specific activity as that of the plasma P. This part, having a length of 

 about 0.9 nun., is entirely newly formed during the experiment. The bulk of the 

 medial part of the dentine was freshly grown as well, while the incisal part, having 

 a length of 1.2 mm., is only partially newly formed with participation of the 

 labelled plasma. About half of the P atoms present in the incisal part of the 

 dentine were not labelled; they must thus be those which were located in the 

 apical or medial region of the incisor before the start of the experiment. The tissue 

 containing these atoms was pushed forward m ioto. Partly before this "slipping" 

 process and partly during it, some of the P atoms of the dentine have the oppoi- 

 tunity to exchange with labelled P atoms and, therefore, the P of the incisal 

 part of the dentine shows an activity which amounts to about 1/3 of the specific 

 activity of the plasma P. We see here an interesting case of tissue formation in 

 which macroscopic aggregates aie "slipped" from one place to another in toto, 

 experiencing only a restricted atomic or molecular replacement. This effect is 

 much more clearly shown in the growth of the enamel. 



The apical and medial parts of the enamel are formed by a calcification process 

 from labelled plasma and, therefore, these parts of the enamel became strongly 

 active. From the fact that the incisal part of the enamel is only slightly acitive, 

 we have to conclude that this fraction is not formed in the course of the experi- 

 ment through a calcification process. Its crystals were formed at an earlier date 

 from non-labelled plasma and the whole fraction "slipped" in toto during the 

 course of the experiment from the position in which it was caltMfied into the 

 place it took up at the end of the experiment. The incisal end of the dentine is 

 probably to a large extent also formed by "shp" in toto of the medial parts, though 

 this conclusion is not supported as clearly by the activity figures arrived at in 

 the case of the enamel. A part of the incisal dentine P bad an opportunity to 

 exchange to an appreciable extent before the "slip" took place and also duiing 

 that process. Enamel P exchanges only to a minute extent [Armstrong, 1940]. 

 It is also of interest to note that the activity figures exclude tlio possibility that 



13* 



