Albert Heim Foundation

Goal and purpose of such a collection

Most of the natural history museums have evolved from private naturalist cabinets dating back well into the 17th century. In the course of history many of these museums changed from sole exhibitions to places of research; so did the Natural History Museum Berne. Scientists in natural history museums are collecting objects from nature to investigate and document, to satisfy their natural curiosity and to increase human knowledge. Man wants to classify, he wants to understand the marvels and relationships he sees in nature. That is how most collections have begun, well before our time.
One of the most distinguished duties of a curator is to preserve those collections for the future and to publish on the collection and the results of his own scientific work. These same reasons stood behind the cynological collections here at the Museum as well. The main question, namely the origins of domestic dogs was one of the first problems that had to be tackled. During the following years -- after the origins have been solved -- problems around the immense diversity of modern breeds as well as problems around the influence of size and shape have arisen.
For centuries many of our modern breeds have been able to evolve without having to serve a direct use -- as most other domestic animals have had to -- only for the pleasure of man. There is no other animal species in the world that shows such a large variability, not only in size and shape, texture and color of the fur, and other even psychic characteristics, but also to a high degree in the shape of the skull. This is one main aspect that makes research on dog skulls so interesting. Research on dog skulls provides interesting insights into the plasticity of animal genetic material.

Some results as examples

Borzoi and Chow-Chow, two completely different dogs

Is the skull of the Russian sight hound, the Borzoi long, narrow or even both? How about the Chinese Chow-Chow? Is his skull broader than average or does he only seems so because his skull is shorter than others? In order to be able to give an answer to such questions a stable measurement representative for the size had to be found. The skull base length that is still used by many scientists is not suited, as it does not only include the braincase but the very flexible facial and palatal region as well. Such a stable measurement was found and tested here at the Museum: It's the "Hirnstammbasis," the length from the oral edge of the Foramen Magnum (Basion) to the boundary of the Pterygoid and Palatine where it joins the Presphenoid. This measurement helped a great deal in describing numerically and thus objectively size and shape of dog skulls. It could be shown, that the above mentioned Borzoi, often referred to as being dolichocephal (e.g. in Miller's Anatomy of the Dog, p.118, 2nd ed.1979), does not possess a longer skull at all, but in reality is only narrow. The Chow-Chow on the other side, often referred as short-faced and lion-like, shows a significant broader skull than would be expected for his size. There is no reduction of the upper jaw in it's skull.
On the other hand, there are breeds that show a strong shortening of the skull. These are mainly breeds from the molossoid group like the Boxer, the Bullmastiff, the Bulldog, The St. Bernard Dog and -- among many other dwarfs -- the Pug. Their skull shape is referred to as brachycephalic. However these breed do not show a reduction of the whole skull but only of the upper jaw. The braincase stays mainly stable and does not show this tremendous variability. These facts give indication of the relationship between the different parts of the skull (facial - palatal - neural) to each other and of the great plasticity of the structures in the region of the Choanae. A different inheritance of upper and lower jaw is obvious when we take a look at all those breeds that show very different lengths of their upper and lower jaws.

A Bullterrier skull with strong clinorhynchy and an English Bulldog (airorhynchic), note the protruding lower jaw in both skulls (prognathism)

The muzzle may not only be shortened as e.g. in the Boxer, but may experience a more or less accentuated dorsal (upwards) or ventral (downwards) bending. The above mentioned sight hounds and several terriers belong here, as we often see a relative strong downwards bending of the muzzle (Clinorhynchy). As we have mentioned previously, a dorsal bending (Airorhynchy) can be seen as well. This is most common with breeds with shortened muzzles. This accentuates the already short muzzle (e.g. Pug, Pekinese, etc.) even more. Such a phenomena can also be detected with the St. Bernard Dog, as this breed too shows an upward bending of the muzzle.

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Size varies tremendously in dogs (Zwergspitz & Irish Wolfhound, note the absence of a Sagittal crest in the dwarf)

One other interesting subject is the dependency of brain size from the absolute size of the skull and the occurrence of a Sagittal crest (Crista Sagittalis). Small dogs have a much larger relative brain size than large dogs. This phenomena is known as Haller's law, which says that small individuals from one species have relative larger brains than their larger relatives. The answer to this law lies in the different relations of bodies and surfaces in different sizes. Small dogs have relative larger body surfaces (surface sinks with the root, volume with the third root) and thus more sensory cells in their skin. Furthermore main cerebral centers may not sink below a certain size as to assure their full functionality. This explains the rather "large" heads of small dogs. This has nothing to do with "intelligence"! (One wonders if the dwarf sized breeds are at their minimum at present, or if there's still a lower limit not yet reached.)
The mentioned Sagittal crest is a bony protrusion whose growth is induced by the muscles of the jaw. Within certain limits the size of the crest may be modified by strain put upon it from the muscles. But much more important is the absolute size of the skull. A small dog will never be able to grow a Sagittal crest for the simple reason that his skull provides so much area for the muscles of the jaw, that the muscles will never even reach the top of the skull. Only the meeting of the muscles from the two sides of the head an top of the skull will induce the growth of a Sagittal crest. Thus this crest is a means for larger dogs to provide sufficient area for their jaw muscles on their relative small skulls. Such and may other laws are easily verified on our collections.

Whom are these results for?

All skulls are measured and read into a database

They are mainly for scientists interested in the development of mammal skull. But the results should also be published for the public interested in dogs, like breeders and judges. We'll try to show this with an example. Many standards insist on a strong or on a weak stop, the stop being the angle between the brain skull and the muzzle. This can very easily be done by selecting such dogs while breeding. The problem is, that a changing of this angle always results in an absolute shortening of skull size. As we have showed previously upper and lower jaw size are not correlated and changing too much the size of the skull will in many cases result in a protruding lower jaw, which is not desired in many breeds. To show such relationships between demands from standards and the consequences is part of our work.

Over 2,000 skulls, and still collecting. Why?

Bullterrier (skulls) changed a lot from 1930 (left) to 1980

In order to make valid statements using statistical methods a large number of measurements on many individuals are necessary. One analysis we undertook a couple of years ago focused on the changing of the Bernese Mountain Dog in the last 100 years and some sex- and size related questions. Although we had about 60 skulls from this breed alone we had only about 7 to 8 per group once we had them separated in male and female, in large and small, in modern and old dogs. One aim of our collections is to be able to document the changes certain breeds make over the centuries. This is the reason we keep on collecting.

Barry in a drawing from 1853 and 4 skulls from St. Bernard Dogs (top: Barry, 2 skulls around 1900 and bottom: present day types)

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