84 



THE BIOLOGICAL BASIS OF INDIVIDUALITY 



We carried out experiments ( 1 ) with rats closely inbred by Dr. Helen D. 

 King at the Wistar Institute; (2) with guinea pigs closely inbred at the De- 

 partment of Agriculture by Dr. Sewall Wright and Dr. Eaton, and later by 

 Dr. McPhee and Dr. Eaton, and lastly, (3) with various strains of mice closely 

 inbred by Mr. Marsh of the State Institute for Study of Malignant Diseases 

 in Buffalo, and others closely inbred by C. C. Little and L. C. Strong and their 

 associates at the Jackson Laboratory in Bar Harbor. A small series of experi- 

 ments with closely inbred chickens, obtained from Dr. H. D. Goodale in Wil- 

 liamstown, have already been mentioned. 



(a) The individuality differentials in closely inbred rats. We shall now 

 discuss, first, investigations made with the closely inbred rats of Dr. Helen D. 

 King, who had developed two distinct inbred strains, A and B ; these had the 

 same origin but they had been bred separately for many generations and thus 

 had acquired in the end distinct genetic constitutions and individuality differ- 

 entials ; in addition, hybrids between strains A and B were obtained. Three 

 series of experiments were carried out with these animals. In the first one, 

 made mainly in 1926, rats from families A and B, belonging to generations 37 



Donor and Host 



TABLE III 

 (Series I) 



Grades 



Combined Grades 



A to A (different litters) 

 B to B (different litters) 

 A to A (brothers and sisters) 

 B to B (brothers and sisters) 

 A to B 

 B to A 



1.82 (24 rats) 



1.92 (27 rats) 



1.68 (12 rats) 



2.55 (24 rats) 



1.67 (18 rats) 



1.57 (19 rats) 



1.87 (51 rats) 

 2 . 26 (36 rats) 

 1.62 (37 rats) 



TABLE IV 

 (Series II) 



Donor and Host 



Grades 



Combined 

 Grades 



A to A (different litters) 



B to B (different litters) 



A to A (brothers and sisters) 



B to B (brothers and sisters) 



A to B or B to A 



Homoiotransplantation in non-inbred families 



(AXB)F< (or F») to (AXB)F, (different litters) 



(AXB)F 4 (or F s ) to (AXB)F t (brothers and sisters) 



A or B to (AXB)F 4 



(AXB)F«to A or B 



1.16 (16 rats) | 

 1 . 65 (33 rats) I 

 2.60 (17 rats) | 

 2.81 (19 rats) J 

 1.37 (32 rats) 

 1.36 



1.29 (12 rats) 

 1.80 (26 rats) 

 1.50 (13 rats) 

 1.39 (13 rats) 



1.49 (49 rats) 

 2.71 (36 rats) 



and 38, 40 and 41, and also 46 and 47 were used ; in the second series made in 

 1930 and 1931, the rats belonged to the 60-67 generations, and in the third, 

 most recent series, made from the year 1939 to 1941, a smaller number of rats 



