1884. Disadvantages of the Upright Position. 
S Prig 3 
paper that it is easy enough zow to remember which veins are 
valved and which are not. Let me present the subject just as it 
perplexed me at first. Nothing could be simpler from the teleo- 
logical standpoint, than that we should have valves in the veins 
of the arms and legs to assist 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 horizontally back- 
ward to the azygos veins? When recumbent these valves are an 
actual detriment to the free flow of 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 
in recognition of their uselessness they do not prevent regurgita- 
tion of blood nor liquids from passing upwards. 
An apparent anomaly exists in the absence of valves from 
parts where they are most needed, such as in the venz cave, 
spinal, iliac, hemorrhoidal and portal. The azygos veins have 
imperfect valves. 
Place man upon “all fours” and the law governing the pres- 
ence and absence of valves is at once apparent, applicable, so 
far as I have been able to ascertain, to all quadrupedal and 
quadrumanous animals: Dorsad veins are valved ; cephalad, ven- 
trad and caudad veins have no valves. The apparent excep- 
tions to this rule, I think, can be disposed of by considering 
the jugular valves as obsolescing, rendered rudimentary in man 
by the erect head, which in the lemur stage depended. The ru- 
dimentary azygos valves may be a recent creation, and an expla- 
nation of their presence may be found in the mutability of the | 
cardinal system. The single Eustachian valve, being large in the 
foetus, has a phylogenetic value. In this connection I would call 
attention to my mention, in Science (New York), June 25, 1881, 
of the probable branchial origin of the thyroid and thymus 
glands. There are many reasons for believing these bodies to be 
rudimentary gills. 
The only reason I can assign for the absence of cephalic and 
cervical valves generally, while the j ugulars possess them, is, that 
the jugular system was the most important to our quadrupedal 
ancestors with dependent heads, hence valves developed in them, 
and that owing to the cranial blood-vessels developing, pari passu, 
with the cranium and its contents generally, largely after man had 
