130 ARBOREAL MAN 



these changes in any detail, since almost every individual 

 manifestation of them that is especially well marked in 

 Man has been seized upon as an example of the alterations 

 due to his orthograde bipedal habits, and, as a conse- 

 quence, the subject has received sufficient attention in 

 the literature of physical anthropology. The heart 

 comes to be suspended from the cephalic end of the 

 thorax, rather than from its dorsal side, and so it rests 

 upon the upper surface of the diaphragm, rather than 

 upon the anterior wall of the chest. Changes in the 

 disposition of the lungs follow harmoniously this read- 

 justment of the position of the heart. 



In the abdominal cavity the same general effects are 

 seen. The viscera sink backwards. The liver is sus- 

 pended more strongly from the lower surface of the 

 diaphragm, and the intestines obtain attachments which 

 sling them from the upper part of the cavity, as well as 

 from its dorsal wall. All these things are adjustments 

 to trunk uprightness — that trunk uprightness which is 

 early brought about in arboreal life — and, as such, they 

 make their appearance long before the stage at which 

 Man walked upright upon his two feet; for it must never 

 be forgotten that the trunk of an animal which climbs 

 up a tree, or sits upon a branch, is just as upright as is 

 that of a Man standing erect. As far as concerns the 

 abdominal and thoracic viscera, a man is as upright when 

 he sits as when he stands, and an arboreal animal which 

 sits and climbs among the branches is in a like case. 



The upright poise of Man has been lauded as one of 

 his greatest distinctions. This praise of human upright- 

 ness has, without doubt, been carried to absurd extremes, 

 so also has the tendency to ascribe to this same uprightness 

 a multitude of human weaknesses and disabilities. This 

 visceral uprightness is no new thing, the readjustment 

 has been gradual, and some measure of it has been very 

 long established. It is easy to overdo the praise of the 

 poise. It is equally easy to overdo the condemnation of 

 it as a cause of many human ills. 



