108 



CARNEGIE INSTITUTION OF WASHINGTON. 



0.00 



9.75 



975 



9.00 



8.75- 



8.50 



825- 



aoo 



weeks- 



Fig. 4. — Curves of average weight development of 

 tumor in each of three families. Ordinates, 

 logarithm of weight in grams. 



vidual of the homozygous dilute-brown (susceptible) race grows the tumor 

 very slowly. An Fi hybrid individual (produced by crossing t\ve dilute- 

 browns to the Bagg albinos) grows the same tumor (dbrB) much faster. 

 By continued back-crossing to the original dilute-brown race, the various 

 back-cross individuals grow the same tumor progressively slower and slower 

 until in the advanced back-cross generations only individuals that grow the 

 tumor at the same slow rate as the original dilute-brown individuals are 

 obtained. 



"(3) The range of variability 

 for the absolute mass of the 

 tumor at any given interval after 

 inoculation is greater in the Fj 

 and F3 generations than it is in 930 

 the original susceptible dilute- 

 brown strain as well as the Fi 

 hybrid generation. It is appar- 

 ent, therefore, that multiple ge- 

 netic factors are concerned in the 

 growth of the transplantable 

 tumor. 



" (4) FamiHes containing indi- 

 viduals growing the same trans- 

 plantable tumor (dbrB) at dif- 

 ferent average growth rates can 

 be isolated and continued by 

 selected matings. Figure 4 con- 

 tains three families, all individ- 

 uals belonging, however, to the F4 generation. These families were sepa- 

 rated from the F2 generation and kept distinct up to the present time. 

 Brother-to-sister matings have been used exclusively." 



In the lines of the dBrA and dBrB, which Dr. Little is continuing at Orono, 

 Maine, five spontaneous tumors have arisen in closely related individuals. 

 One of these is being investigated genetically by Miss B. W. Johnson, who 

 has inoculated over 150 mice of Fi, F2, and back-cross generations. Miss 

 E. E. Jones also is engaged in isolating new single-factor lines for these tumors, 

 by methods so successfully used by Dr. Strong. 



Susceptibility to Alcoholic Intoxication. 



The idea is commonly held that certain groups of men are especially 

 immune to alcoholic intoxication; but whether this immunity is due to indi- 

 vidual accommodation or is a consequence of a selective process extending 

 through generations is not known. During the progress of the alcoholization 

 of white rats it was found that certain ones always required more than others 

 to yield complete intoxication, but no special records were made of such 

 facts. To attempt to analyze genetically such a subtle character as the 

 susceptibility to alcoholic intoxication might seem too difficult were it not 

 for the successful work of Little and Strong in studying the genetic basis of 

 an even more subtle character, namely, susceptibility to implanted tumors. 

 A series of experiments directed toward the formulation of criteria for com- 

 paring the behavior of mice under alcoholic anesthesia has been completed 

 and certain preliminary results have been obtained by Dr. E. C. MacDowell. 

 Over 100 mice have been used in these experiments; of these, 60 have been 



