REPORT OF THE DIRECTOR I9IO 



231 



a new table (table 6) in the following manner. The distance of 

 b.v. I from the orad angle of the IB as measured on the vertical 

 suture of figure 12 (1.80 mm) has been used as a minuend; the 

 distance of the b.v. 2 from the same point or angle of the IB 

 (1.25 mm) has been taken as a subtrahend; the difference between 

 these numbers, the remainder, (0.55 mm) has been entered as the 

 first member of the new table. Taking b.vs. 2 and 3 and treating 

 them in the same manner, we obtain a remainder of o.io mm and 

 enter this as the second member of the table. The other differences 

 expressed in the table were found in a similar manner. The two 

 numbers before any sign of equality designate the b.vs. whose dis- 

 tances (from the orad angle of the IB) were used for minuend and 

 subtrahend. 



Table 6 



Giving, for an aboracl radial group, the difference between distances from 

 the orad angle of the IB (expressed in mm) of a b.v. on the 



left diagonal suture and the 

 next b.v. to appear 



right diagonal suture and 

 the next b.v. to appear 



vertical suture and the next 

 b.v. to appear 



1—2 (1.80— 1.25) =0.55 2—3 (1.25— 1. 15) =0.10 3— 4(1.15— 1.30)=^— .15 

 4—5 (i-30— .70) = .60 5—6 ( .70— .60) = .10 6—7 ( .60— .75)="— -15 

 7—8 ( .75— .30) = .45 8—9 ( .30— .30) = .00 



To quickly, clearly and visually explain table 6, let us take a 

 hypothetical orad radial group. The b.vs. are to appear m sequence 

 with a time interval that shall be 

 the same for all The addition 

 of stereom to the aborad sutures 

 of the basals are supposed to be 

 constantly and regularly in excess 

 of the amount added to their com- 

 mon vertical sutures. This will 

 result in increasing the length of 

 the plate more rapidly than the 

 width. Let us suppose the ratio 

 between verticle and lateral rate 

 of extension to be as 4 to 3. Then 

 when b.v. i has increased its dis- 

 tance from the orad apex of an IB 

 by 4 units, b.v. 2 will have in- 



creased it«; dic:tanrp hv nnlv -7 unite -^^^^ /3 Drawn to represent the b.vs. of 

 HCdSeU US aiSiance Oy Oniy 3 units. a hypothetical group in which the ratio 



Figure 13 shows the condition of "^ ^-^-^l to lateral growth is as 4 to 3 



things when the tenth b.v. has just appeared at the orad apex of the 

 IB and b.v. 9 is just 0.3 millimeters distant from the same 



