THE UPRIGHT ATTITUDE OF MANKIND. 753 
THE UPRIGHT ATTITUDE OF MANKIND. 
Every one must have heard or have read of the supposed perfect adaptation 
of the human frame to bipedal locomotion and to an upright attitude, as well as 
the advantages which we gain by this erect position. We are told, and with 
perfect truth, that in man the occipital foramen — the aperture through which the 
brain is connected with the spinal cord — is so placed that the head is nearly in 
equilibrium when he stands upright. In other Mammalia this aperture lies 
further back, and takes a more obhque direction, so that the head is thrown for- 
wards, and requires to be upheld partly by muscular effort and partly by the liga- 
mentum nuchse, popularly known in cattle as the "pax- wax." 
Again, the relative lengths of the bones of the hinder extremities in man 
form an obstacle to his walking on all-fours. If we keep the legs straight we 
may touch the ground in front of our feet with the tips of the fingers, but we 
cannot place the palms of the hands upon the ground and use them to support 
any part of our weight in walking. Not a few other points of a similar tendency 
have been so often enlarged upon, in works of teleological character, that there 
can be no need even to specify them at present. 
But till lately it has never been asked "Is man's adaptation to an upright 
posture perfect?" and "Is this posture attended with no drawbacks?" These 
questions have been raised by Dr. S V. Clevenger in a Lecture delivered before 
the Chicago University Club, on April i8th, 1882, and recently published in 
the "American Naturalist." This lecture, we may add, cost the speaker the 
chair of Comparative Anatomy and Physiology at the Chicago University ! 
Dr. Clevenger first discusses the position of the valves in the veins. The 
teleologists have long told us that the valves in the veins of the arms and legs 
assist in the return of blood to the heart against gravitation. But what earthly 
use has a man for valves in the intercostal veins which carry blood almost hori- 
zontally backwards to the azygos veins ? When recumbent these valves are an 
actual obstacle to the free flow of the blood. The inferior thyroid veins which 
drop their blood into the innominate are obstructed by valves at their junction. 
Two pairs of valves are situated in the external jugular, and another pair in the 
internal jugular, but they do not prevent regurgitation of blood upwards. 
An anomaly exists in the absence of valves from parts where they are most 
needed, such as the venae cavse, the spinal, iliac, hsemorrhoidal, and portal veins. 
But if we place man upon all-fours these anomalies disappear, and a law is 
found regulating the presence or absence of valves, and, according to Dr. Clev- 
enger, it is applicable to all quadrupeds and to the so-called Quadrumana. Veins 
flowing towards the back — /. e., against gravitation in the all-fours posture — are 
fitted with valves ; those flowing in other directions are without. For the few 
exceptions a very feasible explanation is given. 
Valves in the hsemorrhoidal veins would be useless to quadrupeds ; but to 
