This experiment was made to see whether the allometry formula y=bx^αcan be applied to the growth of bones in inbred mice or not. From above allometric point of view, comparisons among four strains of mice-dd, rr, ss, and C57BL-were investigated, too.
In illustrating with figure, we took the skull length as standard x, and the other parts of bones belonged to the same animal as y, then plotted the value of y corresponding to value of x in double logarithmic graph. Relative growth coefficient α and initial growth index b were calculated by the method of least squares.
The results obtained could be summarised as follows:
1. Allometry formula could be applied to growth of all bones in mice of four inbred strains.
2. Relative growth of bones to skull length was divided into two phases, the first and the second, which have different values of α respectively.
Critical point turning from the first phase to the second was found near 1.200 which is logarithmic value of skull length. This time corresponds with about fourteen days of age in mice.
3. Bones representing positive allometry (α>1.0) were body weight, humeral weight, tail length, femoral length, tibial length, nasal length and parietal length. Many of them showed larger values of a in the second phase than those in the first.
Bones representing negative growth (0<α<1.0) were length of head trunk, skull width, nasal width, prefrontal length and prefrontal width. Thus, these were almost the partial bones in skull.
4. Relative growth of bones to skull length was divided into following three types according to the difference of α value in the first phase and the second.
a) A type: showing much larger value of α in the second phase than in the first. Body weight, humeral weight, length of head trunk and nasal width belonged to this type.
b) A type: showing few differences of α value between the first phase and the second. Tail length, femoral length, tibial length, skull width and nasal length belonged to this type.
c) A type: showing smaller value of α in the second phase than in the first. Prefrontal length, prefrontal width and parietal length belonged to this type.
5. Slight difference of α among mice of four inbred strains was found, but α of nasal width in ss strain was smaller than that of the other three strains.

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