PROTECTION AGAINST HUNTING 



301 



may be considered with confidence because of the high signifi- 

 cance of the figures and the large number of animals studied 

 (see Table I). Fig. 2 gives a good idea of what a typical htter 

 looks like on day 35. 



To analyse these results further, it is necessary to study the 

 factors of variation affecting the observed protective effects 

 against runting. 



(2) Factors of variation 



These factors of variation appear to be concerned mainly with 

 the type of serum utilized for protection, with the dose of serum 

 injected and with the number of injections. 



(a) Type oj serum. Four pools of sera were utihzed in a significant 



ANIMALS TREATED WITH 



70 

 60 



50 i 

 W 

 30 

 20 

 10 

 

 .10 



-20 



Homologous cells 



♦normal serum 



^ Homologous cells 



♦AN-Bi serum 

 — Nothing 

 (norn^l . 

 controls; 



Birth 

 and injections 



, A 



21 28 35 



Days after birth 



Fig. 3. Cumulative curves of mortality (same method as in Fig. i). 

 Protected animals have been treated with serum AN-BI, a serum of 

 low activity; protection is limited to a delayed occurrence of runting. 

 Number of animals aUve on day 7: 42 protected; 39 unprotected; 

 23 normal controls. 



