The success of your whole figure will depend upon the care you bestow on these parts.
They are the real key to its action and proportion. If these points of the shoulders (D) are too far from or too near to the centre line of the body, necessarily the whole figure will be either too wide or too narrow across.
To make sure of these points, divide up the line of the shoulder. On the right we have the end of the collarbone plumbing under the chin to settle for us the length of the line from the neck. Now with it compare the length from B to D, and to make doubly sure see that the shape left on the background is satisfactory.
On the left compare the length of the sweep of the outline of the trapezius (C), from the point where it converges and meets the collar-bone (F), with the length of the line that curves from that point to D ; then with the comparative height and relative positions and slope of the shoulders indicated by the horizontal line across the neck. Make sure, too, that the shape left is correct in form, and in proportion with the head and with the neck.
These detailed instructions may seem to you tedious, but I assure you, you will not regret getting them at your finger-ends.
When you have thoroughly grasped this part of the lesson and know how to apply it, you will have mastered what is considered one of the most difficult problems to contend with—the placing of the head on the shoulders.
In a subsequent lesson reference is made to this problem. I advise you to make a special study of it, not only when you are actually drawing, but at all times. Whenever you find a convenient opportunity of observing people, make a mental note of the setting of their heads on their shoulders, and accustom yourself to looking at the background shapes left between their face, neck, and shoulders ; it will aid your memory, and increase your power of observation and your knowledge.
Let us now return to our drawing. Find under which points of the shoulders the armpits fall, and compare the depth of the passages between the collar-bones and the armpits.