130 CARNEGIE INSTITUTION OF WASHINGTON. 



NEUROLOGICAL STUDIES OF ALCOHOLIZED RATS. 



In order to see if there was any structural difference in the brains of 

 alcohoHzed rats or their descendants that were slow in learning and the 

 brains of the controlled series, Miss Vicari has undertaken histological 

 studies of the brains of the two sets. The comparison of the histo- 

 logical studies of alcoholized and normal rats bears the same relation 

 to their capacity for learning as a comparison of the structure of the 

 testes in the two groups bears to the subject of growth and fertility. 

 Miss Vicari makes the following statement concerning her work : 



"Brains from about 20 of Dr. MacDowell's rats, including tests and con- 

 trols, were collected before leaving this institution. They were fixed for the 

 study of degeneration. In Dr. J. B. Johnston's laboratory at the University 

 of Minnesota this material was dehydrated, cleared, and blocked. I wish to 

 express my appreciation of the suggestions of Dr. Johnson and of his advice 

 as to the treatment and possible method for the histological study of this 

 material; also of his courtesy in offering the use of his laboratory for the 

 preparation of this material." 



The preliminary results of the studies of MacDowell upon alco- 

 holized rats thus confirm, in a general way, the conclusions of Stockard, 

 namely, that alcohol affects not only the soma but also the germ-cells 

 carried by the individual alcoholized, and that these germ-cells are 

 so altered that the individuals developing from them show striking 

 limitations in their capacity for full mental development, and this 

 incapacity shows itself even in two generations removed from the alco- 

 holized individuals. It looks very much as though alcohol was able 

 sometimes to affect germinal material, probably specifically the chro- 

 mosomes, so that it can no longer determine normal nervous develop- 

 ment. The conclusion is so important, as almost the only successful 

 means of modifying the germinal material at will, that the experiment 

 deserves repetition. Further investigation of other methods of modi- 

 fication of the germ-plasm is also desirable. 



ALTERATION OF THE QUALITY OF A POPULATION BY SOMATIC 



SELECTION. 



Experiments with Drosophila. — One of the noteworthy discussions 

 among geneticists in recent years has been that of the possibility of 

 the contamination of genes in consequence of hybridization. This 

 had been tied up with the question of the possibilitj^ of modifying a race 

 in a desired direction purely by a process of selecting somatically. 

 There has, indeed, been no dispute that a mixed race, or one in which a 

 given trait depended upon a number of separate genes or germinal 

 determiners, might be secured in a simpler condition through hybridiza- 

 tion and selection for breeding of individuals whose somatic condition 

 indicated a simple condition of their gametic makeup. The dispute 

 was rather whether genes were, through a process of contamination 

 or other, definitely variable so as to offer an unending stream of condi- 



