The Hybrid Hypothesis

5: The Cranium and the Brain

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From ancient times, the large size of the human brain has been regarded as the crowning distinction of Homo sapiens. And upon first consideration of the idea that humans might have originated via hybridization between pig and chimpanzee, this particular trait seems to pose a major objection to the hypothesis. Why would a cross between a chimpanzee and a pig yield a hybrid with a big brain? The average cranial capacity of a chimpanzee is about 375 cubic centimeters; that of a pig, just 150. If humans are derived from crossing between chimpanzees and pigs, the initial expectation is that the human brain should be of an intermediate size. But, of course, it is not: the average cranial capacity of a human being is about 1,350 cc. Clearly, an explanation in terms of hybrid intermediacy, then, would be unsatisfactory. But, as has already been shown, many other facts are consistent with the idea that a hybridization of this sort actually did occur. Is there then some other explanation? As it turns out, yes, there is.

The human brain is large not only in absolute terms, but also in proportion to body size. This human distinction becomes apparent only during the course of postnatal development. "A variety of sources place the neonatal brain/body ratio at about 12% in both pongids and humans, as in other primates" (Frost¹). However, by adulthood the human brain is about twice as large in proportion to body size as is an ape's (1.8% vs. 0.9 %). These facts suggest that we should look for human characteristics conducive to brain growth outside the womb.

Comparing absolute brain weight with body weight, we find that the former increases rapidly with the latter for small primates, but that for the larger primates a large increase in body weight corresponds to only a small increase in the size of the brain. It is as if the large nonhuman primates have hit a ceiling that limits brain size below a certain level. Only the human brain continues the trend set by the smaller primates. There seems to be some hidden factor allowing brain size in humans to pass through an otherwise impenetrable barrier.

A new type of cooling system. An evaluation of the evidence suggests the human brain was able to break through this barrier because it had a new type of thermoregulatory system. Although brain cells are easily damaged by elevated brain temperatures, they carry out metabolic processes that actually generate heat. If this heat is not dissipated, brain damage will result. If an object, such as a brain or an engine, produces heat internally, it is more difficult to cool when large than when small. Cooling large objects is harder, not simply because they produce more heat, but also because they have a smaller surface-to-volume ratio. It is for this reason that a cooling mechanism may not be feasible for a large engine when the same mechanism is sufficient for a smaller, but otherwise identical, engine. The engine of a lawn mower or a small car can be air-cooled; in a large car or a ship, water-cooling is needed. If air-cooling were the only option, there would be an upper limit on engine size. The same rules must, almost certainly, place limits on brain growth.

Intrauterine development of the human head:

Under sedentary conditions, humans and other primates cool their brains with arterial blood. But cooling cannot be accomplished under all circumstances by ordinary circulation of blood through the brain. Arterial blood is an inefficient coolant. Even before entering the brain, blood in the carotid artery is at, or very near, body core temperature and so is not much cooler than the brain itself. During periods of physical activity, incoming carotid blood becomes so warm that it cannot cool the brain, and even so warm that it would damage the brain—if other cooling mechanisms were not available. In addition, cerebral arteries are in extensive contact with, and absorb heat from, the cerebral veins. This contact causes heat to be fed back to the very areas in need of cooling.² As Cabanac and Brinnel point out

And human beings do have such a mechanism. During exercise-induced hyperthermia, it actively pumps cool blood to the brain from the surface of the cranium. My first inkling that such a mechanism might exist came when an initial investigation of skin structure revealed that humans and pigs share an unusual thermoregulatory system not seen in chimpanzees and other nonhuman primates. This system was described at length in Chapter Six. Its basic units are: 1) a highly vascularized skin, permeated with fine capillaries at a density far in excess of what is required simply to feed the skin; 2) an insulative subcutaneous fat layer pierced by musculocutaneous arteries that regulate blood flow to the skin's surface on the basis of temperature; and 3) a dense population of heat-responsive sweat glands. Comparative anatomists have documented these distinctive features linking human and pig, features that make for a skin that is markedly superior to that of nonhuman primates with respect to thermoregulation, especially with regard to evaporative cooling.

Emissary veins are sensitive to thermal conditions. When the arterial blood feeding the brain gets too hot and the brain begins to overheat (i.e., under hyperthermic conditions), the pattern of cranial circulation changes so that cool venous blood runs rapidly inward through the emissary veins from the superficial evaporative surfaces of the cranium to the brain.⁶ Under normal or cool conditions, the system shuts down; blood flow in the emissary veins slows to an ebb and ceases, or even reverses (flow reversal does not occur in other veins of the body).⁷ In short, the human brain has a water-circulated evaporative cooling system that is actively responsive to thermal conditions. The cranial thermoregulatory mechanism in question here is similar to the cutaneous one discussed in Section 1. In the earlier case, the insulating material was a fatty sheath (panniculus adiposus). In the present case, the skull forms a thermal barrier between brain and environment. Here, the vessels perforating the insulating medium are the emissary veins, there, the musculocutaneous arteries. In both cases the rate of heat flow is actively regulated by the rate of blood flow.

The emissary veins pass into the skull through small holes termed emissary foramina, which are numerous in human skulls, but not in those of apes and other nonhuman primates.⁸ Obviously, when these openings are absent, the corresponding emissary vein must also be absent. The ability of these animals to pump in blood from superficial regions to cool the brain would be limited, then, even if they did possess the efficient evaporative surfaces present in humans and pigs.

Pigs, on the other hand, boast a system of emissary veins that is, if anything, better developed than that in human beings.⁹ Their skin is everywhere densely perfused with sweat glands and capillaries.¹⁰ In these animals, venous plexuses do exist in the upper respiratory tract and they are maintained in direct connection with the brain via numerous emissary vessels.¹¹

The nonhuman primate approach to evaporative cooling is different; sweat plays no significant role.¹² Since the upper respiratory tract of a chimpanzee has no venous plexuses, evaporative cooling takes place in the lungs. But this mechanism is not brain-specific. After cooling in the lungs, blood flows next to the heart. The cooling effect of any evaporation that does occur is therefore distributed equally to all parts of the body, not concentrated on the brain. In human beings and pigs, blood cooled on the evaporative surfaces of the cranium, and carried inward by the emissary veins, is held separate from the general blood supply for direct delivery to the brain.

When the human brain obtained an evaporative water-cooling system like the one in pigs, it escaped thermal constraint. The simian brain continued to deal with hyperthermic conditions in the same old way. Hence, it is easy to understand why brain size reached an upper bound in nonhuman primates as body size increased. But this new, heterotic mechanism would do more than simply allow humans to fully realize an inherent primate tendency to have a large brain. It would permit a more active brain by allowing dissipation of the additional heat generated by an elevated cerebral metabolism. Because it has a super-efficient cooling system, the human brain can utilize oxygen and other nutrients at higher rates than would be possible in an ape. Thus, an assumption of porcine ancestry helps to explain not only the volumetric preeminence of the human brain, but also the more subjective observation that our mental function is somehow qualitatively superior.

Common Chimpanzee or Pygmy Chimpanzee?

Having accounted for the large size of the human brain, we can turn to a consideration of other, less obvious cranial traits. Because there are two types of chimpanzee, treated as separate species, which differ significantly with respect to many such traits, we must first decide which to compare with humans, the common chimpanzee (Pan troglodytes) or the pygmy chimpanzee (P. paniscus). The pygmy chimpanzee has been increasingly known in recent years as the “bonobo." However, for reasons explained below, the name pygmy chimpanzee will be used within within the context of subsequent discussion. Pygmy chimpanzees are quite similar to ordinary chimpanzees, but they are, on average, smaller with respect to most physical measurements.¹³ Average body weight in wild-shot pygmy chimpanzees is just 85 percent of that in P. troglodytes.¹⁴

Any modern chimpanzee that has been genetically influenced by past hybridization would not be an appropriate choice. An ideal analysis would compare the human skull with a skull typical of chimpanzees before the time of hybridization. In this way, all human traits indicating porcine ancestry would stand out. For several reasons, the pygmy chimpanzee appears to be the best modern representative of this ancient type. In particular, there is the empirical finding that the pygmy chimpanzee is far less variable than the common chimpanzee with respect to a broad range of traits. The pygmy chimpanzee is monotypic, that is, it has no recognized subgroups or races.¹⁵ This lack of variability in comparison with the common chimpanzee, which is commonly asserted to have three, or even four, different races, is not merely with respect to external features. It extends also to a wide variety of less obvious characteristics, ranging from sperm morphology,¹⁶ to skeletal measurements, to cranial features,¹⁷ to blood groups and various other genetic traits.¹⁸

This variability is consistent with the idea that the common chimpanzee is itself a kind of hybrid. When two types of organisms come into contact and hybridize, hybrids are at first limited to the region of initial contact. But, with time, the genetic effects may spread outward into surrounding populations because of backcrossing and migration. The introduction of new genetic material into a previously uniform parental population, generates variability. Eventually the entire population can be affected unless some geographic barrier, such as a river or mountain range, happens to protect some isolated group. When the backcrossing is rare or the parental population is relatively large, the amount of variability induced in the parental population will be relatively modest.

Thus, a scenario can be pictured in which an ancient, homogeneous chimpanzee population, similar to the modern pygmy chimpanzee, 1) engaged in hybridization with pigs in North Africa or, possibly, even the Near East; 2) the genetic influence of this hybridization spread south into the previously uniform chimpanzee population generating new variability; 3) this variability continued to spread until it reached an impassable geographic barrier. The most obvious barrier in the region in question is the wide and crocodile-infested Congo River, which in conjunction with its eastern tributaries, today completely separates the range of the pygmy chimpanzee from that of the ordinary chimpanzee (chimpanzees cannot swim).¹⁹

The pygmy chimpanzee (P. paniscus) can thus be interpreted as a genetically stable, geographically isolated enclave of homogeneous chimpanzees that probably resemble ancient chimpanzees (i.e., those that existed prior to the time of the posited cross). Conversely, the common chimpanzee (P. troglodytes) can be thought of as a variable population influenced to some extent by hybridization. In addition, a great deal of evidence suggests that the common chimpanzee hybridizes on an ongoing basis with the gorilla at the present time (read about probable hybridization between the gorilla and chimpanzee). Such hybridization would also tend to alter the northern chimpanzee populations from the ancient type. These various considerations, then, suggest that the pygmy chimpanzee is the best extant representative of what chimpanzees probably were like prior to the hybridization events leading to the production of the human race. Such, at least, is the supposition under the hybrid hypothesis.

Two Types of Cranial Traits

Features distinguishing a human skull from a pygmy chimpanzee's can be conveniently analyzed by breaking them down into two separate sets: those belonging to the cerebral capsule, and those belonging to the noncerebral set. "The cerebral capsule is formed by the tissues which surround, and are intimately responsive to the functional demands of the neural mass [brain]" (Moss and Young²⁰). "Cerebral capsule" is nearly a synonym of braincase. The noncerebral set can be defined as those portions of the skull not influenced by brain growth. Generally speaking, features in the latter category are not in intimate contact with the brain. Most features in the noncerebral set that distinguish a human skull from a chimpanzee's can be ascribed to porcine influence, whereas most differences in the cerebral capsule are best interpreted as consequences of brain expansion. We turn first to characteristics of the second type.

Comparison of a pygmy chimpanzee cranium (left) with that of a human being (right)

The Cerebral Set: Consequences of Brain Expansion

The figure above compares a pygmy chimpanzee skull with a human being's.^a The skulls are viewed from below. Note how all of the features between the incisors and foramen magnum match up from one side of the drawing to the other. The major differences all seem to be related to the obvious expansion of the human braincase. The region where little difference exists could perhaps best be defined as those regions that are not in close contact with the brain.

The correspondence in the drawing is not a result of scaling, which is the same in both skulls. For example, the center of the foramen magnum is about equidistant (on average) from the incisors in both humans and pygmy chimpanzees. Although there is a remarkable degree of correspondence between the two skulls, certain differences are obvious. In humans, the forehead and cheek-bones bulge forward. The whole braincase, especially the rear portion of the skull, has expanded. Any given feature on the portion of the skull adjacent to the brain lies farther from the center line than it does in the chimp skull. The skull is sharply constricted behind the eyes (postorbital region) in Pan paniscus, but not in Homo sapiens. Can these differences reasonably be interpreted as consequences of brain expansion in humans?

Research by Richard Young²¹ of Columbia University shows that the growing skull is, in fact, responsive to intra-cranial pressure. Young studied the effect of brain growth on the shape of rat skulls by manipulating the volume of the cranial contents. In one group of rats he removed a portion of the brain at birth. Survivors developed various degrees of microcephaly as adults. Rats in another group received intra-cranial injections of kaolin that interfered with the drainage of cranial fluids. The result was increased pressure within the cerebral capsule. These rats became macrocephalic. As Young puts it, "Expansion of cranial contents yields intra-cranial pressures which are translated into tensile forces within the [cerebral] capsule. These forces stimulate proliferation of capsular tissues, producing compensatory capsular expansion."²² It is well-known that the soft tissues contained in or attached to the skull govern the growth of the bone adjacent to them. Thus, Taylor²³ showed that, in individuals who lose an eye at an early age, the affected socket never reaches full size. Bony crests normally develop at the point where muscles are attached to the skull and other bones of the body. When Washburn²⁴ surgically removed muscles from young animals, he found that the crests associated with those muscles never developed.

Young's study did more than simply show that intra-cranial pressure stimulates growth of the cerebral capsule. It also demonstrated that certain alterations of the cranium are characteristic consequences of brain expansion. Many features that distinguish macrocephalic and microcephalic rats also distinguish humans from chimpanzees. In macrocephalic rats, the braincase was smooth, globular, enlarged, and thin (all as in human beings). "In the orbital region, rapidly expanding contents displaced the jugum [i.e., cheek bones] anteriorly." The skull base widens²⁵ in rats with extreme cases of macrocephaly and the frontal bone bulges outward as well. The rear of the skull in these rats expanded so that the foramen magnum was no longer at the extreme rear margin of the skull base—in human beings the foramen magnum lies further from the rear of the skull than in chimpanzees.

Of those features distinguishing the human cerebral capsule that we have mentioned thus far, only one is not accounted for by Young's findings: the expansion of the postorbital region in humans. The eyes of rats are not enclosed by orbits as are human eyes. With these animals, then, it is not possible to speak of postorbital constriction. But it is possible to establish a link between postorbital constriction and stunted brain growth by other means: Weidenreich²⁷ notes that the skulls of microcephalic human beings exhibit "pronounced postorbital constriction." He also points out that, in these small-brained individuals, several other features of the cerebral capsule (foramen magnum angle, configuration of forehead and brows, development of air sinuses, placement of temporal lines relative to the sagittal suture, etc.) bear a greater affinity to apes than to normal human beings.

Chin and jaw. The presence of a chin in human beings has been cited by many authors as a distinctive human trait. But so long as the developing chimpanzee is able to keep pace with respect to brain/body ratio, it, too, has a prominent chin, as is evident from examination of the skulls of both fetal and neonate chimpanzees.²⁸ It is only later in development, when chimpanzee brain growth flags and falls behind that of humans, that a chin ceases to be evident. Why the presence of a chin should depend on the size of the brain can easily be explained. If the condyles of a flexible model of a primate jaw are stretched apart, the chin juts out, as in human beings. If instead they are pushed toward each other, the chin recedes and the incisors turn outward, as in the chimpanzee. The lateral expansion of the human skull base forces the jaw joints much further apart than is the case in a chimpanzee. So an expected consequence of brain expansion would a jutting chin. A human jaw is rather similar in other respects to a chimpanzee's (if the teeth are excluded from consideration), the human type falling within the chimpanzee range of variation.

Mastoid process. The mastoid process is a bony bulge on the base of the skull. It lies behind the base of the ear, so close to the skin's surface that it can be felt with the fingertip. It is often asserted in the literature that the size of the mastoid process distinguishes humans from the apes. Thus, Weber²⁹ claimed that "in man alone does the mastoid attain the size of his processus mastoideus, most likely in consequence of the importance of the sterno-cleido-mastoid muscle, which inserts on it, for the maintenance and rotation of the head in the erect position." Standing erect, humans put a strain on this muscle that does not occur in apes and pigs. As has already been mentioned, experiments show that bone tissue responds to such strains by developing bulging processes and crests at the point of muscular attachment.³⁰ It is not surprising, then, if the mastoid process is large in humans.

Neoteny. Noting that baby apes have flat faces without brow ridges, a rounded braincase, and a prominent chin, certain authors have suggested that humans are essentially apes that have somehow retained juvenile characteristics. The retention of such traits is termed neoteny. But baby apes lack multipyramidal kidneys, protrusive cartilaginous noses, light-colored eyes, a panniculus adiposus, epidermal patterning, and a wide variety of other human features. They do, however, have a very high brain/body ratio. The characteristics they share with human beings (but not with adult apes) generally seem to be traits that are consequences of having a large brain (features of the cerebral capsule).

The Noncerebral Set: Features Attributable to Porcine Ancestry

The dimensions of many cranial features, distinguishing humans from apes, show no correlation with brain size. These can be directly attributed to porcine influence.

Nasal bones. Human microcephalics have the large nasal bones³¹ that set humans apart from other primates.³² "In the large size and permanent separation of the nasal bones, man is in marked contrast with all of the anthropoids" (Jones³³). Both the large size and the peculiar protrusion of these bones can be accounted for by a supposition of porcine ancestry.

Occipital condyles. The same line of reasoning explains the large size of these bony prominences in humans relative to other primates (see Figure 8.2). Pigs have large occipital condyles, at least as big as those of human beings.³⁴

Divergent eyes. When an ape skull is viewed in profile, the interior of the orbit (eye socket) is invisible. The same cannot be said of the human skull, where the orbits diverge, not lying perpendicular to the sagittal plane. A pig's eyes are even more divergent than a human being's.

Styloid process. On the base of the human skull, inside the angle of the jaw, is the styloid process, a curved, projecting stalk of bone. In size and shape it is similar to the rib of a rat. "Bony styloid processes, fused with the petrosum, have become a specialization of adult man" (Schultz³⁵). The stylohyoid ligament "continues the styloid process down to the hyoid bone, being attached to the tip of the former and the small cornu of the latter" (Gray³⁶). The styloid process is not initially bony, but ossifies out of the stylohyoid during postnatal development.³⁷ In pigs, the term styloid process is not generally used, but the cranial end of the stylohyoid ligament changes to bone with age and takes on a form similar to that of the human styloid process.³⁸

Gantt (191.8,285) asserts that "Humans have much thicker enamel than any extant primate." Human tooth enamel exceeds that of Pan troglodytes in thickness by about 50 percent. Pigs are artiodactyls—a group as a whole noted for thick tooth enamel.

At one time human premolar roots were considered more primitive than those of apes because they were believed to have fewer roots. Thus, in 1929 F. W. Jones (259.8,321) wrote that "the fact that the upper premolars of man are single-rooted, groove-rooted, or two-rooted, whilst the corresponding teeth in all the Old World Monkeys and Apes are three-rooted, is remarkable." More recent studies have shown that upper premolar roots are sometimes grooved, or double in chimpanzees as well (Pan troglodytes and Pan paniscus). Fenart and Deblock (183.6,Figs. 17 and 21) provide figures establishing this fact beyond doubt. This commonly noted distinction, then, is illusory (or at best statistical) and need not concern us.

The anterior teeth of pygmy chimps of either sex are the same size as those of humans because sexual dimorphism of pygmy chimpanzee teeth is negligible, with the possible exception of canine teeth, which may be slightly larger in females (257.8,46-47).

The enlargement of the molars without comparable enlargement of the jaw forces the teeth together in a tight row that tends to bulge outward. Any outward pressure exerted on the jaw condyles by expansion of the brain case would tend to stretch the left molars away from the right. The result of these two factors would be the "arcuate" or "parabolic" tooth row, which is one of the features distinguishing humans from apes. Oversized molars and cranial expansion would have a similar effect on the dentition of the upper jaw. Cramping of the tooth row would also squeeze shut any gaps or "diastemata" (often seen adjacent to the canines in apes).

The bunodont crowns of human molars, because they are rounded and can slide against each other, contribute to our distinctive manner of chewing. According to Szalay and Delson (545.6,495), "The helical chewing pattern seen on Homo sapiens is not seen in other primates." But Herring and Scapino (233.4,454) state that in pigs "lateral movements are produced by rotation of the jaw as in man, selenodont artiodactyls, and rabbits … Thus it is possible in pigs for the mandible on one side to remain virtually completely adducted while moving laterally with the teeth in contact."

An artist's reconstruction of Nebraska Man, drawn on the basis of a single molar. Source: Forestier, A. 1922. "The earliest man tracked by a tooth: An 'astounding discovery' of human remains in Pliocene strata (A reconstruction drawing by A. Forestier)," The Illustrated London News, June 24, pp. 942-943.

Teeth. Porcine ancestry may also have had an effect upon our teeth. The dimensions and form of our teeth do not seem to depend on brain size. The teeth of microcephalic human beings "do not show essential deviation from the norm" (Weidenreich³⁹). But human premolars do differ from those of apes. The peculiar form of the human premolar has long puzzled both paleontologists and physical anthropologists: "We know of no case in which a comparable specialization [as seen in apes] has been lost once attained [as it supposedly once was in human ancestors], by a reversal to the primitive condition," says a puzzled Bjorn Kurtén, "The specialized premolar of the ape does not change back into the primitive premolar of man."⁴⁰ In artiodactyls, the order to which pigs belong, "the premolars, in contrast with those of perissodactyls, do not usually assume the full molar pattern but remain comparatively simple" (Romer⁴¹). Moreover, among artiodactyls, pigs are considered to have the most "primitive" teeth of any group.⁴²

Many authors have asserted that human incisors and canines (which are termed anterior teeth) have decreased in size during the course of evolution. It is surprising, then, that the absolute measurements of these teeth are almost identical in human beings and pygmy chimpanzees.⁴³ Perhaps the claims that human anterior teeth have decreased in size can be traced to the fact that they look small beside human molars, which are larger than those of chimpanzees.⁴⁴ Consequently, there is a sharp change in tooth size at the molar-premolar boundary in humans that is not evident in simians. Pig molars, too, are quite large relative to the other teeth. In human beings, "the molar cusps are blunt ["bunodont"] rather than sharp ["crenate"] as in apes" (Romer⁴⁵). Pig molars are also bunodont, and so similar to those of human beings that fossil pig teeth have actually been mistaken for those of prehistoric human beings.

One such molar, found in Nebraska in 1917, prompted scholars to name a new genus, Hesperopithecus or "Ape-Man of the West" (see Figures 8.7 and 8.8). This tooth, which was thought to date to the Pliocene (which ended about 1.6 million years ago), became a center of controversy, both in the popular press and in academe. By 1924, prominent English anatomist Sir Grafton Elliot Smith had joined the bandwagon of scientists trumpeting what had by then been dubbed Nebraska Man: "The discovery of this tooth may seem rather a frail and hazardous basis upon which to build such tremendous and unexpected conclusions; and many,

After the furor had continued unresolved for three years, Osborn, then director of the American Museum of Natural History, was prompted to exclaim, "In the whole history of anthropology no tooth has ever been subjected to such severe cross-examination as this now world famous tooth of Hesperopithecus. Every suggestion made by scientific skeptics was weighed and found wanting."⁴⁷ In the same year (1925), this tooth was actually introduced in court as evidence for the defense at the Scopes "monkey trial." Imagine the blush that came to erudite cheeks when further excavation revealed that all the great ballyhoo had been inspired by the humble molar of a pig! "An ancient and honourable pig no doubt," quipped The Times when the news came out, "a pig with a distinguished Greek name, but indubitably porcine."^†

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Works Cited >>

Mammalian hybrids >>

Online Biology Dictionary >>

† The Times, London: Hesperopithecus Dethroned, February 25th, 1928.

CITATIONS:

1. (188.7,199). See also (495.3,445a).

2. (101.85,1011)

3. (101.65,175)

4. (136.2,313 & Plate 2; 166.6, Color Fig. 3; 198.7; 220.1d,596; 506.7,309)

5. (533.6,392)

6. (101.65,173; 101.85)

7. See Chapter 6.

8. (79.3; 79.6; 183.1)

9. (198.7)

10. See Chapter 6.

11. (198.7)

12. (360.8,122). See also Chapter 6.

13. (328.68; 621.9)

14. (119.3; 621.9,362)

15. (602.7,701)

16. (507.2)

17. (80.7, 122.3,Table V)

18. (205.9; 326.15; 379.7; 379.8,266; 531.8,35-39; 589.85)

19. (117.5; 541.9; 580.4)

20. (389.4,282)

21. (610.4)

22. (610.4,399)

23. (557.7)

24. (588.89)

25. (610.4,391)

26. (610.4,390)

27. (589.7,394)

28. (495.7,Figs. 1 & 9)

29. (589.42). Translated in (495.3,447).

30. (301.5; 399.55; 588.89)

31. (589.7,Fig. 41)

32. (158.3,239)

33. (259.8,315)

34. (55.1,300)

35. (495.7,74)

36. (220.1d,322)

37. (220.1d,71)

38. (405.7,147)

39. (589.7,395)

40. (285.5,32-33)

41. (470.4,273)

42. (470.4,273)

43. (119.3; 257.8; 328.68,361a; 415.5)

44. Ibid.

45. (470.4)

46. (527.4,6-7)

47. (414.7)