128
P. R. PAYNE, and ERICA F. WHEELER
proportional to the rate of supply of nutrients across a surface corresponding to the foetal vascular endothelium. The area of that surface will remain in constant proportion to the total surface area of the foetus and is therefore proportional to W 2 / 3 • Thus, the growth rate, ~;, is proportional to W 2 /3,
leading to the equation:
100.0
d.
10.0
/
6
j
cow~1 6
6
I
1.0
J i~Man
~i
P19--) II
01
I~u
~ fj
•
'I'
0>
I
C<:
•
Vl
I
::J
• If
CD
I
0.01
•
2
I
¢ I
'0
Chick'
L
'''".~ .
o t
'?
• J I
'"
I
3' :
,. •
0.001
• Y b r~Rhesus
,
• 'f ~
/ x ,
• 1 ~
I I 0
• x I
J
1 0
00001
J I
I - GUinea Pl9
1 ~
•
000001
I
x
/- Mouse
•
0000001
___ "". ___ .L10
10.0
1000
1000.0
Gestational age (days)
Fig. 1. Foetal weights at different gestational ages, for a number of species.
The curves are calculated from the equation W = a (/-1')3 For data see Table 1
P. R. PAYNE, and ERICA F. WHEELER
proportional to the rate of supply of nutrients across a surface corresponding to the foetal vascular endothelium. The area of that surface will remain in constant proportion to the total surface area of the foetus and is therefore proportional to W 2 / 3 • Thus, the growth rate, ~;, is proportional to W 2 /3,
leading to the equation:
100.0
d.
10.0
/
6
j
cow~1 6
6
I
1.0
J i~Man
~i
P19--) II
01
I~u
~ fj
•
'I'
0>
I
C<:
•
Vl
I
::J
• If
CD
I
0.01
•
2
I
¢ I
'0
Chick'
L
'''".~ .
o t
'?
• J I
'"
I
3' :
,. •
0.001
• Y b r~Rhesus
,
• 'f ~
/ x ,
• 1 ~
I I 0
• x I
J
1 0
00001
J I
I - GUinea Pl9
1 ~
•
000001
I
x
/- Mouse
•
0000001
___ "". ___ .L10
10.0
1000
1000.0
Gestational age (days)
Fig. 1. Foetal weights at different gestational ages, for a number of species.
The curves are calculated from the equation W = a (/-1')3 For data see Table 1