Canine Brachium

Dogs have disconnected shoulder bones (lacking the collar bone of the human skeleton) that allow a greater stride length for running and leaping.Consequently this specialization shrinks the biceps, as the scapula lacks the bony coracoid process onto which it can anchor. The supraspinatus muscle enlarges, filling out over half of the scapula surface. The deltoid muscles shrink as they lack the bony ridge of the clavicle from which to emerge, and the triceps take on a more important role in translocation. Most interesting is how the radius has pronated and then locked itself in, although it hasn't fused like a horses radius and ulna .

Shoulder Girdle

The Shoulder girdle is in essence a pelvis that has evolved to allow for the brachia apparatus, i,e,. mechanical specialization of the humerus and shoulder that facilitates the the needs of  the pronated hand and opposable thumb. Freed from it's primary purpose of translocation and isonomic channeling (dispersion of gravitational force) which defines the structure of the pelvis , the Sacrum ,Ilium and Ischia have now separated and the scapula takes shape- becoming the Ischia and Ilium of the shoulder. These free floating "pelvic halves"allow for a greater range of movement than a fixed pelvis could ever allow..Clearly it is evident that he pubic bone of the pelvis is analogous to the clavicle of the shoulder girdle. With a bit of imagination it can also be observed that the Coracoid Process of the Scapula is analogous to the Pubic Bone of the Pelvis.

Biceps Brachii

This week in the Ecorche class we covered the Biceps Brachii and the adjacent musculature of the scapula...the Brachialis, the Coracobrachialis, the Pectoralis Minor , and the superior aspect of the Serratus Anterior- all assisting in the movement of the scapula and the upper arm.

Congruency of Biceps

This illustration is from lecture blackboard notes from the Artistic Anatomy class that I teach at the Barrett Art Center in Poughkeepsie

A third Class Lever in Diagram

The Biceps Brachii of the upper arm and the Biceps Femoris of the upper leg share a offer an interesting shared function. The contraction of both muscles result in the action exemplified by a third class lever- where the Resistance ( gravitational vector or weight), lies between the Fulcrum(joint) and the Effort (Muscular contraction). Like a crane, this lever facilitates the maximum concentration of force against gravity, and is the primary force in trans-location of the body. What is fascinating is that the both muscle groups are located anterior and posterior of each other. Evolving from quadriped animal ancestors whose translocation imperative was the use of limbs oriented in the same direction for running, into an upright standing biped whose survival imperative was increased by their ability to grasp objects,the upper limbs migrated to face the front. As a result of this, the rotation of the thumb occurred- the first metacarpal of the thumb rotating along with its corresponding wrist bone, out of plane with the other four metacarpals. It would also appear that this entire process occurred after the earliest animal ancestor of man still had some use for a minimally grasping foot since the human foot shows evolution away from any grasping imperative. The tarsal bones have evolved to distribute weight more efficiently therebye resulting in fewer bones in the ankle. If this earliest ancestor had perfected its running imperative to survive, the hand as a grasping mechanism and the entire bipedal strategy would never have occurred.