Journal of the Academy of Natural Sciences of Philadelphia . f to two others already united, thesystem will evidently have three partitions, namely, one proceeding from the unionof the first two films, and two from the union of each of these films with the three partitions will necessarily terminate at the same arc of junction, andsupposing that they still have spherical curvatures, it will result that at three linesof junction of each of them with two of the films the angles will still be of 120° ; itwill result, moreover, for reasons already given, that at the arc of junction of
Journal of the Academy of Natural Sciences of Philadelphia . f to two others already united, thesystem will evidently have three partitions, namely, one proceeding from the unionof the first two films, and two from the union of each of these films with the three partitions will necessarily terminate at the same arc of junction, andsupposing that they still have spherical curvatures, it will result that at three linesof junction of each of them with two of the films the angles will still be of 120° ; itwill result, moreover, for reasons already given, that at the arc of junction of thethree partitions with each other the angles will be also of 120°. This being pre-mised let us see by what means we can trace the base of a system of this kind, aswe have traced, Fig. 23, that of a system of two films. After having described, , the bases of the first two films, bases having for centres c and c, and for radiithe lengths given which we will again designate p and p, let us take commencing 354 MORPHOLOGY OF THE CEREBRAL Fig. 25. flV at the point s, where these two bases meet, and on the radii s c and s c, twolengths s f and s f, equal to one another and to the radius p of the thirdbase, then from the points c and c as centres, and with the lengths c f and c f as radii, let us trace two arcs of a circle, theirpoints of intersection on c will be the centreof the base of the third film, a base which wewill then describe with the radius p. Let usin effect suppose the problem solved and thisbase traced. If we draw from the point nwhere it terminates in one of the former theright lines n c and n c, which will be respec-tively equal to p and p, these lines will makebetween them an angle of 60°, like the right liness c and s c; whence it follows that the triangle c nc will be equal to the triangle c s f, in which s cand s f are also respectively equal to p and p, and thus c c will be equal to c f, forthe same reasons the triangle c v c will be equ
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