IN THE VENTRICLES OE THE VERTEBRATE HEART. 
497 
made, a cone is produced whose anterior wall consists of four layers (the poste- 
rior wall consists of three), the lines composing these layers having different 
directions, as represented at Plate XVI. diagrams 4 & 5, and at Plate XII. 
figures from 1 to 8 inclusive. See pages 484, 485, & 486. 
Diagram 2, Plate XV. Double sheet of net, the one sheet (F G Y) being laid upon the 
other (A B X) at a slight angle. Shows how when the two sheets thus arranged 
are rolled up together the cone produced is bilaterally symmetrical, as might 
be imitated (Plate XVI.) by placing the cone marked diagram 5 within that 
marked diagram 4. It also shows how the lines composing the sheets enter 
the apex in a whorl in two distinct sets (Plate XVI. diagrams 7, 10, & 12, E F), 
after which they wind from the apex towards the base, likewise in two sets 
(Plate XVI. diagram 11, X Y). See pages 486 & 487. 
G. Point which when the sheets are rolled into a cone corresponds to its 
apex, that portion of the uppermost sheet marked X assuming the 
position of the anterior musculus papillaris (Plate XVI. diagrams 8, 9, 
& 11, Y), that portion of the lower or undermost sheet marked X 
taking the place of the posterior musculus papillaris (Plate XVI. dia- 
gram 11, X). 
PLATE XVI. 
Diagram 3. Sheet of net with threads of wool drawn through it at wide intervals, rolled 
up in a cone as explained, the cone being placed upon its apex. Shows how 
lines originally of the same length make fewer turns of a spiral from winding 
round wider portions of the cone. It also shows how the apex of the cone 
may be enlarged by removing in succession the lines which make the greatest 
number of spiral turns, and which, curiously enough, overlap the lines which 
make the fewest number of turns. See pages 484, 485, & 486. 
Note . — The lines in this diagram correspond with the lines in diagram 1, 
Plate XV., bearing similar letters. 
Diagrams 4 & 5. Anterior and posterior views of a cone produced by rolling a sheet of 
net upon itself, similar to that figured in Plate XV. diagram 1. In the 
cone marked 5, that portion of the sheet which forms the base (KB) has 
been folded upon itself in an outward direction, to cause the internal lines 
to reverse their direction and become parallel with the external ones, with 
which they unite. 
Note . — These diagrams show how by one portion of the sheet overlapping 
another several layers are produced, the lines composing these layers having 
different directions. They also show how the layers or overlappings are con- 
fined to different regions or localities, just as in the left ventricle, and satis- 
factorily account for the ventricular wall tapering towards the base and the 
apex respectively. See pages 484, 485, & 486. 
