The Company of Biologists

Table 1.

Allometric equations for the scaling of organ masses and metabolic rates in mammals

Organ	Organ mass	SMR	Organ mass×SMR
Liver	0.033M_b^0.87	2861M_b^−0.27	94.4M_b^0.60
Brain	0.011M_b^0.76	1868M_b^−0.14	20.5M_b^0.62
Kidneys	0.007M_b^0.85	2887M_b^−0.08	20.2M_b^0.77
Heart	0.006M_b^0.98	3725M_b^−0.12	22.4M_b^0.86
Remainder	0.939M_b^1.01	125M_b^−0.17	117.4M_b^0.84

Organ	Organ mass	SMR	Organ mass×SMR
Liver	0.033M_b^0.87	2861M_b^−0.27	94.4M_b^0.60
Brain	0.011M_b^0.76	1868M_b^−0.14	20.5M_b^0.62
Kidneys	0.007M_b^0.85	2887M_b^−0.08	20.2M_b^0.77
Heart	0.006M_b^0.98	3725M_b^−0.12	22.4M_b^0.86
Remainder	0.939M_b^1.01	125M_b^−0.17	117.4M_b^0.84

Data taken from Wang et al.(2001).

M_b, body mass in kg; SMR, specific metabolic rates in kJ kg⁻¹ day⁻¹.

These relationships raise the question of why organs masses and specific metabolic rates decline with increasing body mass.