Poetic Science Goethe Mix Tape

Bone Examinations

Observations of the Intermaxillary Bone

Reading Goethe’s piece “An Intermaxillary Bone Is Present in the Upper Jaw of Man as Well as in Animals” was interesting, but it was frustrating to not be able to see the bones of which he was speaking. Considering I had never handled a human skull to observe the bones in the jaw, I could not imagine the differences he was describing. It was very interesting and rewarding to be able to observe these things for myself at the Exhibit Museum of Natural History.

I observed most of the skulls that were laid out, but I was most interested in the human skull versus the skull of the chimpanzee and the skull of the gorilla. These were my most detailed drawings, and I spent the most time finding different comparisons I could make.

I first compared the skull of a mature chimpanzee with that of an adolescent chimpanzee. The most obvious thing I observed was the difference in the distance between the nose and then tip of the mouth. After comparing the intermaxillary bones in each, I decided this was not the source. The intermaxillary bones were proportionally equal in size. In the adolescent chimpanzee, the molars start right beneath the nose. However, in the older bone the molars start much further forward, accounting for the lengthened snout.

I then observed the gorilla and human skull. The most striking difference between the gorilla and the chimpanzees was the alignment of the first four teeth. This is due to the curvature of the intermaxillary bone. In the chimpanzees the front four teeth are curved, more like the humans. In the gorilla, the front four teeth are aligned almost completely straight. I found it interesting that the curvature in the intermaxillary bone in the chimpanzees were more similar to the humans than the gorillas. However, in the human skull, the intermaxillary bone is located almost directly beneath the nose. This is not the case in the chimpanzee or the gorilla, in which the intermaxillary bones are located a good amount past the nose.

I also observed that the palates in the chimpanzee were very shallow in comparison with the gorilla and the human. The human skull had the deepest palate of all however. In researching the function of the palate, I discovered the hard palate is responsible for the formation of sounds, particularly the “t”, “d”, and “j.” This could explain the differences in the concavity of the palate. Since the human skull had such a deep palate, this may be due to the ability to make these sounds in speech, something less important for gorillas and chimpanzees.

Intermaxillary Bones in Various Mammals – Notes

Looking at the selection of skulls we examined, the first thought, from an anthropic standpoint, would be that the skulls of other the other animals seem like elaborations and expansions of the human skull. Our jaws, compared to the distended shapes of those of, say, porpoises or dugongs, appear small, compact, and relatively simple, and our teeth seem similarly diminutive and similarly uncomplicated.

The explanation for human jaw proportions (from the Discovery Channel; make what you will of that) is that the invention of fire and therefore of cooking made the chewing of food easier. The necessity of biting through and masticating raw meat gone, jaws could shrink without unpleasant evolutionary consequences. The results of that not happening, I think, are visible in the skulls of the other primates we looked at. Both the gibbon and the gorilla had particularly large canine teeth, suggesting (assuming that, like humans, gorillas and gibbons are omnivorous) that the chewing of meat was the real issue at hand, the problem of how to deal with fibrous grass and foliage presumably requiring more radical adaptations.

Aside from size, I surmise that humans and the above-mentioned other primates eat in much the same way. The incisors and canine teeth tear or scissor off pieces of food, which are passed backwards to the molars to be ground down prior to swallowing. While not identical, teeth of these kinds in humans, gibbons, and gorillas are extremely similar; molars are all broad and roughly cylindrical, canines terminate in a point, and incisors narrow to an edge. Another similarity: the near-invisibility of the premaxilla as a distinct bone separate from the rest of the jaw. By contrast, the premaxilla, in the remainder of the animals, is generally quite distinct.

In grazing animals, such as the horse, and rodents, such as the capybara and the beaver, the premaxilla protrudes, like the bow of a ship, from the remainder of the jaw, which contains the molars. The reason for this, I think, is because there is a greater distinction between the roles the teeth play. In humans (and presumably other primates), teeth can perform each other's tasks somewhat interchangeably: incisors aren't wholly unsuited to chewing; molars just do a better job. Molars, depending on the food, can cleave off pieces as well. Contrast this with how a grazing animal would eat: the incisors clip off pieces of plant matter, which is passed backwards for prolonged chewing. In that case, a long row of molars, set far back from the mouth's front (possibly allowing for biting and chewing with the same movement), is more efficient at processing large amounts of grass than humans' compact jaw layout could ever be. A similar sharp distinction in function seems apparent in rodents, whose large incisors appear to play the predominant role in eating, shaving or tearing off small, manageable chunks of food. The molars are greatly reduced, possibly to (as in hamsters) allow the cheeks to serve as storage space, possibly because the individual pieces of food being dealt with aren't particularly substantial. Human mouths here occupy a “jack of all trades” role, with teeth and jaw portions not only shrunken but less differentiated.

Premax Lab

Premaxillae as a Unifying Characteristic

In his research on premaxillae, Johann Wolfgang von Goethe sought to establish an archetype for all animals (Goethe 111-112). The premaxilla, his chosen bone to focus on, is an interesting choice as it has many morphologies depending on the feeding habits and other needs of the mammal. For example, a reasonably basic version of the skull is shown in beavers, whose primaxillae are similar to many other groups in the class Mammalia.

Here one can see the basic structure of the beaver, whose premaxilla is located next to the nasal. The premaxilla is relatively small in comparison to surrounding structures like the prominent zygomatic arch.

In other mammals, evolution has driven unusual premaxilla morphologies. For example, grazing animals like horses have a significantly longer premaxilla. This is probably due their diet, which consists of grasses. In order to graze safely, long premaxilla, maxilla and nasal bones are required to push the eye back. Having a backset eye ensures that the horse will be able to see over the grass and watch for predators effectively while grazing. This supports Goethe’s assessment that an animals diet affects what type of premaxilla it has (Goethe 112). While Goethe was correct in this instance, there are also non-dietary reasons for changes in premaxilla shape.

A more extreme version of premaxilla elongation is seen in water mammals like porpoises and dolphins. In the specimen viewed in class, the premaxilla was clearly visible stretching from the front of the skull back to the top of the head. This extreme stretching of the premaxilla helps to allow the dolphins and porpoises to push back their nose holes. This morphology is necessary in underwater mammals because it allows a minimized surface area to be above the water when breathing. Breathing through the top of the head, as opposed to the front of the face, lets underwater mammals barely come above the surface, reducing risk of predation and exposure to air.

While Goethe’s work on the premaxilla wasn’t fully accepted by scientists of his time, we now know that premaxillae are one of the unifying charachteristics of animals. While they may vary in size and shape, the general structure remains an archetype as Goethe hoped.

Sources:

Goethe, Johann W. Scientific Studies. Trans. Douglas Miller. New York: Suhrkamp Publishers, 1988.

Museum of Natural History Bone Lab

Museum of Natural History Bone Lab

This lab in the Natural History Museum was able to open the eyes making connections to the texts of Goethe that we have been reading and the physical bone structures under question. It was an experience which helped me better appreciate the things that Goethe accomplished in his studies of the intermaxillary bones also called the premaxillae. It was pretty unreal to see the structures in the skulls of the different species and then compare them to each other. The position of these bones and how they functioned for the specific species was a very interesting spectrum to see.

There were six different skulls of animals that I sketched in this lab, in addition to the human skull that I more completely sketched. The six animal skulls that I observed were a gorilla, a young chimpanzee, an older chimpanzee, a bison, a fox, and a harbor porpoise. These six animals I did not make complete sketches of the entire skull, just ones that better showed where the intermaxillary bones are located and what it looks like. I made sure to sketch the roof of the mouths of the animal and human skulls in order to compare the intermaxillary bones across the different species. There were some very interesting comparisons to be made.

The intermaxillary bones in humans are located on the roof of the mouth one on each side of the centerline of the mouth. They contain the incisors and are very hard to see in humans, if at all. The one skull that I looked at, I was able to barely make out the faint cracks that run along from the center of the mouth to a spot in between the last incisor and the canine. The sutures were very hard to spot because of how thin they were. In humans the intermaxillary bones must fuse earlier in life under a decent amount of pressure in order to be that thin.

I also studied the skulls of some animals that are closely related to humans, the chimpanzees and gorillas. In these species the intermaxillary bones are very easy to spot clearly running from the center of the mouth to a spot in between the canines and the last of the incisors. The line created by the intermaxillary bones and the bones of the rest of the mouth in the chimpanzees ran more perpendicular to the centerline of the mouth than they did in the gorilla. This makes sense because the snout of the gorilla is a little bit more elongated than that of the gorilla. I also looked at the skull of the both a younger and an older chimp to see the differences between them. The sutures created between the intermaxillary bones and the rest of the mouth are more readily seen in the younger chimpanzee. They are more jagged and appear like fissures in the bone. The sutures in the older chimpanzee look as if they have been put under a greater pressure and have been fused together. These lines are much smoother, as compared to the fissures of the younger chimpanzee.

Next I looked at the intermaxillary bones of a bison. These bones were very different then the premaxilla of the chimps and gorillas. The primates use their incisors to a great extent, so a lot of pressure is put on them when eating. In that way the intermaxillary bones are small, compact, and do not extend to far from the skull. This is different with bison though. They do not use their incisors too much because they are more of a grazing animal. Instead the bulk of the force is put on their molars. This seems to be the case at least, because the premaxilla of the bison is very long and protrudes out a great distance from the bulk of the skull, as shown in the sketch. It seems to be very fragile and not take a lot of force. They start at the roof of the mouth, like in the primates, and loop around very intricately, continuing up the front part of the face under the nostrils.

The fox skull that was looked at was almost a combination of the bison and primates in terms of premaxilla shape. The intermaxillary bones were angled a bit forward like the gorilla skull, and also headed up the front of the face like the bison. The interesting features of this skull were two little holes in the roof of the mouth. These are depicted in the sketch and their purpose is unknown.

The last skull that was looked at was that of the harbor porpoise. This skull looked like a mammal skull that had been pulled out long like taffy. This skull was unique because its intermaxillary bones are extremely long. They looked like two white strips on the top of the long snout. They were very thin and looked as if they were not used too much in terms of load bearing during eating.

It seems as if there are differences in the intermaxillary bones that correlate with differences in the types of food that the animal eats. Humans and animals like the primates have very stout intermaxillary bones that are held close to the skull. This would more than likely due to the use of the front incisors when biting into food to tear it. The canine skulls like the fox are similar to the primates except that their premaxillae are lengthened a little bit and not as stout, which might have to do with the fact that they use their canines more when eating. The bovine animals like cows and, in this experiment, bison have very long intricate intermaxillary bones since they do not use their incisors at all. They use their molars to grind up all the plant matter that they eat.

Bone Lab

Goethe observed that, in fetus skulls, there appeared a bone which scientists at the time didn’t accept was present in humans. Yet Goethe’s findings of the premaxillary bone are accepted today, though it is much harder to make out the premaxillary in adult skulls than those which Goethe observed. Because bones fuze as an animal grows and matures, sometimes the premaxillary bone fuzes to itself and to the maxillary bone. An example of this fusion can be observed in figure 5. In the adolescent lion skull, the suture between the premaxillary bone and the maxillary bone is clearly defined. However, when looking at the adult lion, this distinction is not so clear. This fusion may occur for many reasons, scientists are not quite sure. One reason is that the skeletal system is dynamic, that is, it is always changing. So when more pressure is placed on the suture as time goes on, this suture may just close up. Scientists have also suspected that bones may fuze together for greater stability.

Despite the fact that bones do indeed fuze together, the premaxillary bones are much more visible in other mammals than in humans. This is due to their primary function as a structure; that is, to hold the incisor teeth. However, in some mammals like the manatee, they have a leathery pad on top of their mouths which is also connected to the premaxillary bone. While it isn’t exactly known why some mammals have a more defined premaxillary than others, there seems to be some correlation between diets and the size of the premaxilla in mammals. In animals that rely heavily on gnawing with their incisors, such as the beaver, the premaxillary bone is much more pronounced (figure 7 and figure 8). Whereas in animals that use their incisors similarly to how man does, like a chimp, the premaxillary bone is much less defined (figure 6). In animals like the anteater which don’t even have teeth or which don’t use them to gnaw or tear, there is no premaxillary bone present at all. A sloth, which is similar to the anteater, similarly does not use its incisors for gnawing or ripping, thus, a sloth has no need for a large premaxillary bone as evident in figure 1.

There are also different branches of the premaxillary bone. These branches are either well defined or not. In the lion, for example, these different branches are well defined. Figure 3 demonstrates one such branch and figure 4 demonstrates the other. These two branches are the palatal branch and the nasal branch, respectively. These branches can also be seen in a beaver (figure 8). However, because the premaxillary bone is much more defined in the beaver, it is larger. Thus, these two branches are not as distinct.

The shape and scale of the premaxillary bones differs between animals. A whale skull (figure 9), for example has premaxillary bones very different to that of a lion. Figure 10 is of premaxillary bones in a whale and figure 2 shows a premaxillary bone of a lion. These two animals eat in very different ways, so it is understandable that their premaxillary bones would be shaped differently. While this bone may be used to demonstrate differences between animals, it may also be used to describe how animals may be similar. Families of bats, for example, are distinguishable in many ways, one of which is by the size and shape of the premaxillary bones.

Goethe’s method is thus still widely used today; pure and simple observations are necessary in order to note similarities and differences between families and species. While genetic evidence is more widely accepted, genetic evidence is not always available to use for identification. A solid classification is based on both observation and genetic evidence. Either way, it shouldn’t make that much of an impact because, as Professor Phil said, “there is one and only one history”.

Premaxillary Bone

This week we had the opportunity to examine skulls at the Exhibit Museum of Natural History here at the University of Michigan. The skulls came from 20 different species similar to those that Johann Wolfgang von Goethe described in his research on the premaxillary bone. In his work, Goethe argues that the premaxillary bone is present in humans just as it is in horses, lions and primates¹. Therefore, our class went to view a collection of skulls in order to compare the presence and shape of the premaxillary bone across many different species of animals and try to find an underlying reason for the different forms.

The first set of skulls I looked at were those from a bison, cow, and deer (pictures of a cow are shown from the side and below – the premaxillary bone is labeled 4).

All three of these animals had elongated premaxillary bones (about 15 cm in the bison) below the nasal cavity that wasn’t connected to any teeth. These animals are all herbivores, with a diet consisting mainly of grass, berries, and twigs. This led me to postulate that herbivores might all have similarly elongated premaxillary bones that weren’t connected to any incisors. Although incisors were present amongst the bottom row of teeth, the corresponding spot in the top row was completely void. Professor Phil Meyers, our host, explained that instead of having teeth here, these animals have a flat, hard patch due to the premaxillary bone. Although this explains the absence of the teeth, it still does not make much sense to me. The incisors are used for tearing, which would be important for pulling bark off a tree or grass up from the ground. Therefore, it seems that these animals should have incisors in both the bottom and top rows of teeth.

In order to further investigate the lack of incisors in herbivores, I moved on to examine the skull of a horse (pictured, left) and tapir, which are both herbivores as well. To my surprise, the premaxillary bones did not have the same form as in the previous three animals. In both the horse and the tapir, the premaxillary bones were elongated to the same degree, but were connected to 6 front teeth. Looking at different types of rodents, which are also herbivores, the premaxillary bones were elongated in beavers and capybaras (pictured, right), but instead of being connected to 6 teeth, the premaxillary bones were connected to only 2 teeth. Thus the hypothesis that the premaxillary bone was not connected to any teeth in herbivores and the idea that there is a relationship between the type of food eaten and number of teeth connected to the premaxillary bones were quickly proven false.

In omnivores, such as humans and a few types of primates, the premaxillary bone is extremely small and sometimes hardly noticeable. This is especially the case in adults, hence the difficulty Goethe faced in proving its existence in humans. I was able to observe this in the macaque, gibbon, gorilla and chimpanzee skull samples. All of these animals, which have similar eating habits to humans, have extremely similarly shaped premaxillary bones – their lines of fusion in the mouth were hardly noticeable and they were connected to the front 4 teeth. I found this to be the same for lions as well, which are primarily carnivores (pictured). To look at the connection between diet and size of the premaxillary bone, I looked at a sample of a sloth skull. Alas, sloths, which are herbivores, had premaxillary bones that resembled those of the primates and lion without front teeth. Therefore it seems that there isn’t a cut and dry connection between diet and the presence of incisors or the shape of the premaxillary bone.

After reflecting though, I came across the idea that there is a connection between the way animals find their food and the size of their premaxillary bone. Animals such as the cow, bison, horse, and rodents don’t use hands like primates and sloths to search for food. Instead they use their noses or snouts to poke around and identify foodstuff. This corresponds to the elongated premaxillary bones in these animals. The premaxillary bone functions to form a snout that can be used for digging or poking around. The skulls of a dugong (pictured) and manatee serve to fit into this mold. Both of these animals are herbivores, have well-developed premaxillary bones, and especially in the case of the dugong, use a snout to dig up sea grass for food. Although not entirely fool-proof, it seems a slight connection might exist after all.

¹ Goethe, Johann Wolfgang von. “An Intermaxillary Bone is Present in the Upper Jaw of Man As Well As in Animals.” In Scientific Studies, edited and translated by Douglas Miller, 111–116. New York: Suhrkamp, 1988.

Bone Lab

This week our class had the privilege of spending our hour-and-a-half observing Premaxillary Bones in numerous animals, thanks to the direction and assistance of Professor Phil Meyers. Not only did Professor Meyers facilitate our understanding of the premax structure with his rich knowledge and tangible examples, but he supplemented the entire discussion with fascinating information regarding other animals and the functions/uses of other body parts (I will never look at a whale again without thinking that part of their mouth used to be used to make women's undergarments).

The beginning of our discussion of the Premaxillary Bone consisted of reading about Goethe's suggestion that humans do in fact have the bone. Since seemingly all other animals had the bone, Goethe insisted, in accordance with his theory of universality in nature, that humans must have it as well. Many other scientists of the time disagreed with Goethe's assertion, but as it turns out, Goethe was actually right.

Given that humans do have the bone – although it's seemingly difficult/impossible to distinguish – I was most interested in the Premaxillary Bones of monkeys. Conveniently, I was sitting in front of two Macaques, a baby from 1925, and an adult from 1873. Not to my surprise, I found it hard to distinguish the Premaxillary Bone from the Maxillary Bone in both Macaques, but I noticed a significantly larger split in the roof of the mouth of the baby Macaque. If my estimation of where the Premaxillary Bone ends and the Maxillary Bone begins is accurate, it appears that the Premax was 1 cm in the baby Macaque and 1.5-2 cm in the adult Macaque.

Baby Macaque

Adult Macaque

I was determined to see a more blatant Premax following the Macaques, and the one I found to be the easiest to see was in the Harbor Porpoise, which appeared to have a defined Premaxillary Bone of about 18 cm long. At this point I figured that whether an animal had the Premax or not depended on whether or not it had teeth (We had learned that the anteater, which does not have teeth, does not have the Premaxillary Bone). I then saw, however, that the Humpback Whale had a significant Premax, but also does not have teeth, so based on the lab and what we have learned about the Premax thus far, I don't think that there is a definite determiner in whether or not an animal has the Premaxillary Bone.

Harbor Porpoise

Anteater

Humpback Whale Premaxilla

Premaxilla in Myrmecophagidae (anteaters)

Source: Animal Diversity Web, http://animaldiversity.ummz.umich.edu