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320

Cunningham Memoirs.

point. This we may take (Parchappe, Broca, Welcker, Merkel, and others)
to vary between 5 and 1 cm., and considering that the measurements are
made with pressure the lower limit may be taken as the working amount to
deduct.

I have found by trial on the cadaver that this mode of application of
the indices is sufficiently accurate to be a reliable guide. Having obtained
the temporoparietal depth, it only remains to measure off the parietal
depths as given by Prof. Cunningham, and which for convenience are
reproduced here.

Temporo-Parietal Depth = 100.



Parietal Depth.

Period of Growth.







Eight.

Left.

7-J to months foetuses,

60-6

61-4

Full-grown foetuses, ....

61-0

62-4

First year of life, .....

64-6

62-5

4 to 5 years, .....

65-9

65-4

11 to 15 years,.....

69-7

68-8

Adults, ......

69-7

68-5

(The figures given for the adult will serve to check off the localization of the
posterior limb of the fissure, as given on p. 144.)

Until we are in possession of a large series of facts, determined by
Professor Cunningham's mode of preparation, and by relative measurements,
the above-described method of ascertaining the position of the central
portion of the posterior limb of the fissure of Sylvius can only be regarded
as of approximate value. The same point can also be obtained, after the
situation of the squamous suture is noted, by means of the Sylvio-squamous
Index given in tabular arrangement on page 141; but in this case the same
source of error prevails, viz. the temporo-parietal depth.