14 



Scientific Proceedings (ioi). 



average, tend to contain one lethal factor after 100 generations — 

 which means about four years in Drosophila. The rate of change 

 for the X in Drosophila is thus about one detectable muta- 

 tion in four years. This immediately shows us that Drosophila 

 must have a different rate from some other organisms — man for 

 example — for if the X chromosome of man mutated at anything 

 like a similar rate, all the X chromosomes in a female would 

 contain several lethal factors by the time she was ready to re- 

 produce, and none of her sons would be viable. 



The rate of one mutation in four years is the rate for the 

 whole chromosome. It is of greater interest to know the rate for 

 the individual factors. There is good reason to believe that there 

 are at least 500 factors in the X chromosome of Drosophila — 

 probably many times that number. But, taking this undoubtedly 

 much too low minimum figure, it is easy to see that, if 500 factors 

 show only one mutation in four years, each individual factor 

 must on the average show a change in its composition only 

 once in 2,000 years. (Yet this is in the mutable Drosophila.) 

 It will be interesting to observe the difference in mutation rate 

 in different organisms and under different conditions. 



6 (1466) 



The influence of lactic acid upon the metabolism of the dog. 1 



By Graham Lusk and H, V. Atkinson. 



[From the Physiological Laboratory, Cornell University Medical 



College.] 



Lactic acid, when given to a dog, causes the same increase 

 in metabolism that is noticed when a similar amount of alanin 

 is administered. It was also noted that the metabolism was in- 

 creased after giving 500 c.c. of water in which there was 2.5 c.c. 

 of Liebig's extract of beef, whereas the administration of 150 

 c.c. of water had no influence whatever. When a large quantity 

 of water was given about 100 c.c. per hour were eliminated in the 

 urine. This indicates that for the transport of a large volume 

 of fluid through the circulation increased energy is needed. 



1 A brief report of this work was also published in the Compt. rendus de I'academie 

 des sciences, 1919, 168, No. 20, 1012. 



