198 



MORTEN SIMONSEN 

 Table III 



Index of hunting . Specimen litter demonstrating the calculation of the 

 INDEX. The litter is newborn (C3HX DBA/2) F^ injected with 25 million 



ADULT C3H SPLEEN CELLS 



* For animals dying at time t between days 5 and 30, this index is expressed as 

 (^— 5)/(25)x 0-40. If the test animals survive the period of observation, the index is 

 determined as the body weight ratio between test animals and Htter-mate controls at 

 day 21. 



We next want to construct a single scale of indices which 

 extends from o- 40 to i • 00 for milder degrees of ranting, and from 

 0*40 to 0-00 for more severe runting. The extension upwards 

 is easy. It comprises survivors only, and these are given the index 

 determined by the ratio of their body weight, at day 21, relative 

 to normal litter-mates. There are no such animals in Table III. 



The extension downwards requires that an animal which dies 

 at day 29 gets a lower index than o- 40, and that the lowest possible 

 index is given by a mouse which dies at day 5. We may defme the 

 index of runting in these cases by the equation : index of runting = 

 (^ — 5)/ (25) X o- 40. This gives an index of o for a mouse dying at 

 the 5th day, and an index of (25)/ (25) x o- 40 = 0- 40 for a mouse 

 dying at day 30. 



It is hardly necessary to emphasize that this is purely an ad hoc 

 procedure for the purpose of the present experiments. No attempt 

 has yet been made to determine if this mamier of expressing 

 severity of runting would withstand the requirements of a dose- 

 response assay. 



The data of Table IV show the indices of runting, as determined 



