434 



ON INCREASE IN SIZE 



[PT. Ill 



2-9. Growth Constants 



Brody is not the only worker who has applied the differential 

 calculus to embryonic growth-curves. Teissier and Lambert & 

 Teissier suggested simultaneously that this should be done, but their 

 work was quite theoretical. However, Schmalhausen published in- 

 dependently at almost exactly the same time a paper in which it 

 actually was done. He criticised Minot's method of calculating 



Dayso 10 20 30 40 50 60 70 so 90 100 no 120 iso uo i50 16O i70 18O 



c 

 o 

 O 



8 



CO 



18 28 38 



58 68 78 



Age 

 Fig. 55 a- 



108 118. 128 138 U8 158 



" mittlerer prozentualer Zuwachs " in arbitrary time-units from exactly 

 the same point of view as Brody. Thus, he says of the Minot method: 

 "the larger time intervals we take, the bigger the error will be. With 

 equal time intervals, the error will be bigger the bigger the rapidity 

 of growth, and this will in fact lead to altogether misleading figures 

 for the early periods". We need not follow Schmalhausen's reasoning, 

 which led him to adopt the calculus as a better assistance in studying 

 growth-curves, for we have already examined and approved the 



