The Body of the Dog (The Chest)

The Body of the Dog | When one thinks of movement in the canine, thoughts often go first to the angulation of the fore and rear quarters of the dog. While these areas certainly have a major role in motion, there are other structural areas that influence a dog’s movement. Some areas influence movement in subtle ways and other sections of the structural whole can have more of an impact. What role does body of the dog (chest) play in its movement? Have you ever thought about what your breed’s standard has to say about this part of their anatomy and why? Does it say a little or a lot, or nothing at all?

The rib cage is made up of thirteen thoracic vertebrae and thirteen pairs of ribs. The floor of the chest (sternum or brisket) is formed by a row of eight bones called the sternebrae (sternum or breastbone), which are connected by cartilage. (See Figure 1.) The prosternum is the longest bone of these sternebrae. It is located at the front and it juts out ahead of the shoulder joint (the joint were the shoulder blade articulates with the upper arm). The other end of this chain of bones of the sternum (under the body) ends with the xyphoid process. (See Figures 1 & 2.)

This entire structure is referred to as the thorax or chest, and often more simply as the rib cage. It serves several functions, including the protection of the vital organs contained within its bounds (most notably the heart and lungs) and the initiation of a bellows-like action necessary for breathing. It also acts as a supporting structure upon which the forequarters are “hung.” The chest also determines the width of the dog.

Let’s take a closer look at the terminology used when describing the body of the dog, and how its make and shape can influence the dog’s movement.

There are basically four shapes of the canine chest; the oval, the oval-tapered (egg-shaped), the round or barrel, and the narrow chest. (See Figure 3.) The round chest has the greatest volume of any shape and the least surface area. Plus, the ribs are structurally stronger. The other shapes have a decrease in the volume of the chest cavity as the chest narrows, but it also deepens to allow room for the heart and lungs.

The oval chest provides a flat surface for the oscillation of the shoulder blade and is the most commonly found shape of the chest in the dog. An oval chest is one that is deeper than wide. (See Figure 4.) From the German Shepherd Dog Standard: “Chest—Commencing at the prosternum, it is well filled and carried well down between the legs. It is deep and capacious, never shallow, with ample room for lungs and heart, carried well forward, with the prosternum showing ahead of the shoulder in profile. Ribs well sprung and long, neither barrel-shaped nor too flat, and carried down to a sternum which reaches to the elbows. Correct ribbing allows the elbows to move back freely when the dog is at a trot. Too round causes interference and throws the elbows out; too flat or short causes
pinched elbows.”

The oval-tapered, or egg-shaped, chest provides the same flat surface for the shoulder blade movement, and the narrowing of the bottom of the oval helps to permit leg convergence under the body of the dog, which is especially important in the dwarf breeds. (See Figure 5.) From the Pembroke Welsh Corgi Standard: “Body—Rib cage should be well sprung, slightly egg-shaped and moderately long. Deep chest, well let down between the forelegs.”

The round chest of the Bulldog gives maximum volume for the heart and lungs, and this wider chest spreads the front legs farther apart, providing for more stability in the stance. (See Figure 6.) From the Bulldog Standard: “Body—The brisket and body should be very capacious, with full sides, well-rounded ribs and very deep from the shoulders down to its lowest part, where it joins the chest. It should be well let down between the shoulders and forelegs, giving the dog a broad, low, short-legged appearance. Chest—The chest should be very broad, deep and full.”

In contrast to the Bulldog, the narrower oval chest of many dogs varies from breed to breed, and also varies in the breadth of the chest. It is particularly found in Sighthounds such as the Greyhound, as it allows the shoulder blade to oscillate more efficiently on their narrower, more flat-sided chest. (See Figure 7.) The shape of the Sighthound is more aerodynamic, which helps to ensure that they can reach and maintain their high running speeds. From the Greyhound Standard: “Chest—Deep, and as wide as consistent with speed, fairly well-sprung ribs.” From the Whippet Standard: “Brisket very deep, reaching as nearly as possible to the point of the elbow. Ribs well sprung but with no suggestion of barrel shape. The space between the forelegs is filled in so that there is no appearance of a hollow between them.”

The climate in which a breed worked may also have some say in the shape of the chest, as the rounder chest has less surface volume per pound of weight, and thus, less heat loss—an advantage in cold climates and for smaller dogs. The oval chest has more surface area, an obvious advantage in hot climates. The majority of breeds fall somewhere in between the narrow and the round chest (in varying degrees of an oval) and most have a reduction of chest size immediately behind the elbows that then expands to full volume, allowing for maximum heart and lung room, and permitting efficiency of movement of the forequarters.

Each of the 13 ribs of the chest articulate with a thoracic vertebrae at the top. (See Figure 8.) All but the last four ribs articulate with the sternum at the bottom. (See Figure 9.) Between these two portions is the main body (shaft) of the rib. The shaft of the rib is basically oval in shape, and the first six or seven ribs are flattened somewhat near the top of the rib when viewed from the side. This slight flattening of the outside of these ribs forms a smooth surface over which the shoulder blade moves when the dog is in motion. The remaining ribs behind this first group of somewhat flattened ribs are much more rounded, forming the remainder of the rib cage. The bottom ends of the first nine ribs are made of cartilage and are joined to the sternum by cartilaginous joints. The 10th–12th ribs do not join the sternum, but are usually attached to one another by cartilage at the end of the rib. The last rib is usually unattached and is most often called a “floating” rib. (Refer to “Cartilage”
in Figure 1.)

One of the most important functions of the rib cage is to provide the mechanics for breathing. The unique shape (and the connection between the ribs and the thoracic vertebrae) allows the ribs to swing forward and outward, and is called a “Bucket Handle” movement as it resembles the handle of a bucket. When the ribs swing outward and forward, the internal capacity of the chest cavity increases, allowing the lungs to expand and a breath to be drawn into the lungs. This act of inspiration is active, whereas exhalation is passive and occurs when the muscles relax and the ribs move backward and inward. (See Figure 8.) This action speaks volumes to the importance of the correct shape of chest for every breed of dog, and it’s why attention to detail in the make and shape of the rib cage is so vital. Small variances in the shape of the rib, especially where it attaches to the spine, can affect the dog’s ability to get enough air into the lungs when in motion. The phrase “spring of rib” comes from the shape of the rib and rib cage as it “springs” or arches out from the spine and continues to flow into a rounded rib cage, especially in the latter half of the ribs behind the scapula. Volume comes from depth, but it also comes from the width of the ribbing, and a “slab-sided” dog is one in which the ribbing in this area is more flattened instead of rounded. Some breed standards call for a narrower rib cage (slightly sprung or slightly rounded), but they usually state that the chest should be deep and extend well to the rear, thus providing enough capacity for heart and lungs.

The make and shape of the chest can have a major effect on the fore assembly. Depending upon the shape of the chest, the front assembly can be pushed forward or outward and contribute to evasive motion of the front feet, such as moving wide or paddling or winging. A dog that is slab-sided is too narrow in width of ribs or the ribs are flat, with little spring of rib. This causes the chest to be narrow across the entire length of the body when viewed from above. These dogs are inclined to move “close” coming and going; where the foreleg tries to incline toward the centerline but the column of support is broken at the pasterns, and where hocks lead the feet to move parallel and close to each other without crossing over. The Bulldog’s round chest places the muscular, very heavy shoulders widespread and slanting outward, giving stability and great power. Bulldoggers describe this shoulder assembly as “tacked on” to the body. The Bearded Collie standard calls for ribs that “…are well sprung from the spine but are flat at the sides.” This is understood in a dog that has a body described as “…long and lean, and, though strongly made, does not appear heavy.”

I hope this article inspires you to think about your own breed in a somewhat different manner. Like the old song lyric, “the thigh bone’s connected to the leg bone,” I hope that this closer look at a part of the body we don’t often think about causes you to study your standard and understand how your breed was supposed to perform the function for which it was developed. When pondering this, you should also know the terrain and the climate in which your breed was expected to work, in order to fully understand why the breed is formed the way it is. All of this information helps you to better understand why your breed differs from others of its kind. Learn about the whole dog so that you can then see how the individual parts interact. Learning the hallmarks of your breed is the only way we can preserve our beloved breeds for future generations.

If you have any questions or comments, or to schedule a seminar, contact me via email at jimanie@ welshcorgi.com.