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Design Handbook on Animal Research Facilities Using Static Microisolators 
2.3 
Justification of Dimensions of Simulated Mouse Object 
From Gordon, C.J. 1993. Temperature Regulation in Laboratory Rodents , page 57. 
“...Because heat exchange between an animal and its environment occurs over its exposed 
surface area, expressing metabolic rate in terms of surface area is often preferred. Whereas body 
mass obviously is a simple parameter to measure, surface area must be estimated using a power 
relationship with certain assumptions: 
where SA is surface area in square centimeters, W is the species weight in grams, and the 
constant k, termed the Meeb coefficient, is species-dependent, with a wide range of intraspecies 
values, ranging from 6.9 to 13.3 for mouse, 7.2 to 13.0 for rat, and 7.1 to 10.8 for guinea pig 
(Altman and Dittmer, 1962). These are incredibly wide variations, and they imply that a rodent 
of a given weight could have as much as double the surface area as another of the same weight, 
depending on which value of k is used in the calculation. Clearly, there has been considerable 
error in the determination of surface area. For rodents such as the mouse, rat, and guinea pig, a k 
value of 9.0 appears to be most accurate for calculating surface area (Herrington, 1940). 
One problem with using surface area as a denominator in metabolic calculations is that the 
exposed area (i.e.. the skin where heat is transferred from the animal to the environment) can 
vary depending on the animal’s behavior. For example, in a hot environment, rodents assume a 
sprawled posture to maximize surface area, whereas in the cold, the limbs are pulled close to the 
body to minimize the exposed surface area. Thus, the animal’s thermoregulatory behavior affects 
heat loss per unit of exposed surface area, while heat loss per unit body mass remains relatively 
constant.” 
Using k=9, which is most accurate for rodents, the surface area will be: 
If use 7/8" diameter PVC pipe to represent mouse diameter, therefor two ends would be: 
SA=kW 067 
SA = 9.0x(20)°' 67 =67 cm 2 
67cm 2 x 0.155 = 10.38in 2 
X7T = 1.2 in 2 
10.38-1.2 = 9.18 in 2 
