No. 495] NOTES AND LITERATURE 



207 



groups of chemicals have been discovered which are efficient in 

 the treatment of trypanosome infections. They are: (a) benzi- 

 din dyes, (6) basic triphenyl-methane dyes and (c) arsenical 

 compounds. In experimental animals complete cure has appar- 

 ently been effected by maximum doses of these compounds. With 

 lesser doses and prolonged treatment the parasites may disappear 

 from the blood for a time, but later on make their appearance 

 again. Those which recur have undergone a pronounced change 

 in their biological characters and constitute a strain resistant to 

 the therapeutic agent employed. Such a strain manifests chemo- 

 resistance of a specific character towards the particular sub- 

 stance used to develop it and an increased resistance towards 

 other compounds of the same group. On the other hand, the 

 development of resistance towards one group causes no increase 

 whatever in the resistance towards other groups. By continued 

 experiments, however, a strain has been produced manifesting a 

 triple resistance, specific towards each of substances employed. 



Chemo-resistance, once acquired, persists unchanged while the 

 resistant trypanosomes are passed through normal animals even 

 for one hundred and forty transfers extending over fourteen 

 months. This has been cited as strong evidence of the trans- 

 mission of acquired characters. The specificity of the resistance 

 is very striking. After an experimental animal has been inocu- 

 lated with a mixture of two resistant strains and is then treated 

 with a substance towards which one of the elements is resistant, 

 the other element will disappear from the blood, but the resistant 

 strain will remain and develop unchecked. Indeed, the two 

 strains remain separate and capable of isolation after repeated 

 passages through infected animals. Or. in other words, a strain 

 with double resistance or with modified resistance does not arise 

 as the result of infection with a mixture of two resistant strains. 



Henry B. Ward. 



ANIMAL BEHAVIOR 

 Recent Work on the Behavior of Higher Animals — There exist 

 to-day two main centers for the strictly scientific and experi- 

 mental study of the behavior of the higher animals. One is 

 at Harvard, led by Yerkes, the other at Chicago, under Watson. 

 Excellent work appears at times from other quarters, but it can 

 usually be traced to the influence of one of the two men named. 

 There is a third independent center for such work at Clark 



