Rate of Pulse in Man. 



97 



Mutants should be selected whose loci are properly spaced — not 

 so close together that the error of random sampling is excessive, 

 nor so far apart that double crossing over occurs between them. 

 (3) When the amount of double crossing over between two distant 

 loci is accurately known, data involving them can be used by 

 making the appropriate correction. (4) The data must be ob- 

 tained under uniform conditions, special attention being paid to 

 the age of the parents, constancy and suitability of temperature, 

 and to freedom from genetic modifiers of crossing over. (5) Any 

 experiment involving more than two loci should figure only once 

 in the calculation of each particular region of the chromosome. 

 (6) Data for each region should be adequate in amount as judged 

 by the laws of probability. (7) If slightly different positions are 

 indicated by two or more independent experiments, then a mean 

 position should be calculated in accordance with the amount and 

 value of the different sets of data. (8) The framework of the 

 map having been constructed on the basis of the most significant 

 loci, each remaining locus is interpolated as accurately as the 

 amount and reliability of data permit. 



57 (1432) 



Effect of position of body on the length of systole and diastole 

 and rate of pulse in man. 



By Warren P. Lombard and Otis M. Cope. 



[From the Physiological Laboratory of the University of Michigan 



Medical School.] 



There is need of a practical method of determining the con- 

 dition of the heart muscle in man. The contraction period of 

 other muscles is lengthened if they are fatigued or degenerated, 

 and this may be true of heart muscle. An accurate determination 

 of the length of systole might be of use, provided its normal rela- 

 tionship to the heart rate and the ordinary variations were known. 



At the Minneapolis meeting of the American Physiological 

 Society December 28, 191 7, the writers reported that they had 

 studied the length of systole and diastole in man, by recording 

 the carotid pulse and measuring the systole from the beginning of 



