QUANTITATIVE LAWS IN REGENERATION. I. 



By JACQUES LOEB. 

 (From the Laboratories of The Rockefeller Institute for Medical Research.) 

 (Received for publication, November 22, 1919.) 



Regeneration consists in the growth of resting cells or buds as a 

 consequence of the removal of parts of the body. Two problems 

 are, therefore, involved in this phenomenon; namely, first, the 

 quantity of growth which is measured by the mass of the regenerated 

 organs, and, second, the problem of inhibition, or the fact that 

 regeneration or growth of the resting cells or buds does not take 

 place without removal of part of the body. 



I. The Law of Direct Proportionality between the Mass of Sister Leaves 

 of Bryophyllum and the Mass of Roots and Shoots Produced by Them. 



The writer had already shown that equal masses of sister leaves of 

 Bryophyllum calycinum when isolated from the rest of the plant 

 produce in equal time equal masses of shoots under equal conditions 

 of temperature, moisture, and illimiination.^ The following measure- 

 ments show that the same law holds also for the production of roots. 

 In order to be able to measure the mass of roots correctly, it was 

 necessary to let the roots develop in water. Part of a leaf was dipped 

 into water, and in the wetted notches shoots and roots grew out 

 rapidly, thereby preventing the growth of roots and shoots from the 

 non-submerged notches of the leaf. In order to get accurate measure- 

 ments of root production it was necessary to determine the dry 

 weight of the roots. In addition, the dry weight of the leaves and 

 of the shoots was also determined. The experiments lasted usually 

 from 4 to 5 weeks in order to get larger masses of roots and to diminish 

 the error in determining the quantity of regeneration. The organs 

 were dried in an oven at a temperature of between 100° and 110°C. 

 for about 24 hours. 



^ Loeb, J., Bot. Gaz., 1918, Ixv, 150. 



297 



