THE UNIQUE MAMMAL 41 



they constitute an overwhelming majority of the vote when 

 the "normality" or "type" issue is up for consideration. There is 

 no absolute or transcendental normality or type. This is a point 

 well to remember when we get into the more complicated realms 

 of human biology such as sociality, political behavior, and the 

 like. The second generalization about human variation is that 

 the differences in respect of various separate characteristics of 

 the individual are statistically correlated in greater or smaller 

 degree, so that, for example, if a man has extra long arms he is 

 also likely to have extra long legs. This phenomenon of corre- 

 lation is an expression of the integration that is so important a 

 feature of the organism in contrast to the inorganic, and that 

 makes the living organism something more than and different 

 from the simple sum of its component parts. 



The third generalization is that the total range of variation 

 that exists relative to any characteristic and species stakes out 

 the limits of viability, or survival, relative to that characteristic in 

 the whole frame of reference that constitutes the pattern of that 

 particular form of life. Here we enter upon somewhat new 

 territory, and illustration and example will be required. Every- 

 one knows that while the pulse rate per minute varies from 

 individual to individual, and from time to time in the same indi- 

 vidual, it does so within quite narrow limits. Furthermore every- 

 one knows that if the individual's life is to continue the rate of 

 heart beat cannot transcend these limits. In the state of normal 

 health and well-being these limits are roughly from some- 

 where around 50 beats per minute to 90 odd beats per minute. If 

 under the influence of disease or injury the heart rate goes out 

 much or long beyond these limits, the individual goes out too, 

 for good and all. So then a rule can be stated about variation in 

 human pulse rate that no living human being ever has a pulse 

 rate more than m times greater than the pulse rate of any other 

 human being. When a numerical value has been assigned to m 

 we shall have a limit of viability of the human organism in 

 respect of individual variation in this characteristic, rate of 

 heart beat. By taking into account a sufficient number of obser- 



