Biological Foundations of Language
Eric H. Lenneberg+
Harvard Medical School
III. BEHAVIORAL SPECIFICITYAND THE PROBLEM OF PLASTICITY
(1) The problem
A discussion of the embryology of behavior is likely to raise more questions that it answers. For instance, how can we explain the results of animal training? A dog can learn o fetch, point, heel, jump, etc., upon his master’s commands. Pigeons are trained to run in a figure eight. Rats can learn to press a bar that produces a marble which they must carry to another machine that delivers a pellet of food when the rat drops the marble into a slot. In short, there appears to be an infinite variety of novel tasks certain animals can learn to perform and an even greater number of possible combinations in which we can have an individual associate a certain stimulus with a certain response.
胚胎學的行為討論很有可能所提出的問題會超之所答。例如：我們如何解釋動物訓練的結果？狗能透過主人的指導學會拿物、指物、緊追、跳等動作，鴿子經訓練能飛八字型，老鼠經訓練能壓下橫槓取出彈珠，牠們需要再將彈珠投向另一台機器孔內得到一粒粒的食物。簡而言之，動物似乎能學會實行許多不同的新任務，得到更多不同可能組合，甚至我們可讓個體連結某種刺激與回應。
On the other hand, all dogs bark, all pigeons coo, all rats squeak. Behavior that is so universal among all members of one species cannot be the consequence of either training or unique environment circumstances that produced it.
另一方面，狗吠叫、鴿子咕咕叫、老鼠吱吱叫，這些行為普遍於相同物種，不是經由訓練結果或特定環境下產生而來。
Here we have grouped behavior in such a way as to make it appear as if there were two entirely different types: one specific to a species, and one the result of plasticity. Although this dichotomy conforms to a popular conception, it is actually untenable. Specificity and plasticity are phenomena that may co-exist. Most behavior of higher animals is in some aspects specific to the species and still be the result of circumstance. Biological factors are ever present, and even the degree of plasticity is an evolutionary phenomenon, the product of biological conditions.
在這裡我們將行為分類成兩種完全不同的類型，一為物種特性，另外一種為可塑性結果。即使這兩種區分符合一般想法，但卻站不住腳。生物特有性和可塑性是可能共存的現象，許多高等動物在某些方面的行為是物種特有，甚至可塑性的程度也成為進化現象，一種生物型態的成果。
The problems of species-specificity and plasticity of behavior are particularly relevant to investigations of speech and language because, on the other hand, this behavior is specific to the species Homo sapiens, and on the other hand, there is an obvious degree of plasticity that accounts for the divergences between modern natural languages. A general discussion of this theme against a background of a wide variety of zoological and physiological phenomenon will help us in obtaining a better biological perspective of man and of verbal behavior.
因物種特性問題和行為可塑性特別與說話能力與語言研究相關。一方面，這項行為是人類特有的；另一方面，可塑性程度說明現代自然語言分岐性。一般討論這個主題常以不同廣泛動物學和生理現象為基本，幫助我們獲得人類生物學與口語行為兩者更好的未來發展。
Instead of considering behavior in a complex, molar way, let us concentrate on motor and sensory processes alone. Every animal has biologically given modes of moving and perceiving; its behavior must be dependent on the ways in which it is internally wired, so to speak. How is this internal constitution related to the behavioral patterns we study in psychology? How is plasticity affected by the ways an animal is arranged biologically?
不將行為想得太複雜化，讓我們只將重心放在運動神經和感知過程上。每種動物在生物學上有移動和接收形式；牠的行為必須取決於所謂的內部線路。這種內部構造要如何與心理學的行為模式做連結呢？可塑性由什麼因素影響動物生物學地排列呢？
Weiss (1950) and Sperry (1958) have summarized the results of many experiments in which the neoro-muscular connections in animals were surgically rearranged. Various kinds of lower vertebrates were operated on with the general aim of interfering with peripheral motor and sensory mechanisms. For instance, limbs of larval salamanders were transplanted and allowed to regenerate in the “wrong position or wrong side” of the animal; or eyeballs of frogs were served from the optic nerve and made to regenerate after 180 degree rotation. In all these experiments motor and sensory functions could be restored after surgery, but in each case the behavior was inappropriate to the demands of the situation. After the rotation of the eye the frog would jump to the right side in order to catch a fly that was presented to it from the left; or the misplaced limbs of the salamander would make the animal walk backward instead of forward. In no case could the animals operated on learn to overcome the anatomic disarrangement. Experience, purpose, reinforcement, or whatever other mechanisms we might postulate, were of no avail. Here we obtain a picture of highly rigid mechanisms with an apparent absence of plasticity. But let us guard against overgeneralization.
Weiss (1950) 和 Sperry (1958) 曾概述許多動物肌肉神經經由外科手術重新排列的實驗結果。許多不同低等脊椎動物大多受手術讓周邊運動神經和感知機制受到干擾，例如：移植蠑螈幼體的分肢，並將其移到錯誤的位置或身邊；或者把青蛙的眼珠從視覺神經內分割，並將眼珠180度旋轉。以上實驗預想運動神經和感知功能在術後即恢復原樣。但在每個實驗中，行為和情況要求是不相符的。轉動青蛙的眼球後，原本要捕捉左方的蒼蠅，牠卻跳到右方捕捉，而接錯分肢的蠑螈則只會向後走而不會向前走。從來沒有動物能學會適應解剖後的錯置。經驗、效果、援助，或任何我們認為可以用的機制全都沒有幫助。在這裡我們得到較多固定結構的資訊，而可塑性的部份明顯地較少提及，但是我們不能過度概化。
The lowest immature vertebrates behave as if they had put one (or very few) motor-behavior or perspective patterns. Even if we switch limbs or sense organs to unnatural positions, the original behavior pattern and sensory integration soon reasserts itself – although it is now useless to the animal. As long as tissues function, they cause the animal to behave in the one and only pattern with which it was endowed.
最低等幼年脊椎動物表現就好像牠們有一種（或一點點）運動肌肉行為或知覺反應模式。即使我們將牠們的分肢或感知器官移植到不正確的位置，原本的行為模式和感知整合很快地重新自我判定，即使現在對這些動物無效，不過只有生物組織能讓這些動物表現出一種或只有一種牠們所賦有的行為模式。
In higher forms a multitude of patterns emerges. The patterns are no longer indivisible units but may be thought of as consisting of constituents or behavioral components. They are the building stones for the complex patterns which are available and which enter into a great many combinations, thus producing the infinity of tasks for which a higher animal can be trained. But if we examine the motor coordination itself, if we study the sequence in which muscles contract, limbs flex, and trunks rotate, we can often discover species-specificities on the level of motor patterns. Also in perception there are species-specific thresholds and species-specific limits to pattern perception. The greatest degree of specificity is probably found when we make inventories of complex reflexes, since these combine both sensory and motor peculiarities.
較高層級時，更多行為模式產生。這些行為模式不只是不能分割的個體，更認定為不同要素或不同行為組織成分組合而成。就像是用石頭砌築，不同複雜式樣都是由許多組合完成，因此高等動物經訓練後能完成無數的任務，但如果我們要檢視牠們的運動神經協調，可從肌肉契合度、肢體彎屈、肢幹轉動一系列的動作來研究，我們常發現物種特有的運動模式，也可從感知看出物種特有始創或物種特有限制感知模式。最高層次的特有性可從一些已存的複雜反射動作找到，因其中包含了感官和運動肌肉結合之特有性。
This specificity is always present, whereas plasticity is a matter of degree. The two phenomena are discovered by different approaches of study. They are not mutually exclusive types of behavior. Nor can plasticity be define as “dependent upon experience or upon environmental influence” while specificity is not so dependent. All of life is dependent upon environment and may be modified by it. Thus the notion
“dependence upon environment” (which by implication is the same as “dependent upon experience”) is not a useful criterion for the classification of behavior.
因此特有性是一直存在的，然而可塑性卻要相當的程度，我們可從不同現象的研究找到探討這兩種不同現象的主題。他們並不是互相特有形的行為，也不是說可塑性可定義為『仰賴經驗或環境影響』，而特有性則不需仰賴任何事物。
Let us follow the problem of motor coordination further and discuss the concept of plasticity with respect to this aspect.
讓我們延續運動肌肉協調的問題，進一步重點討論可塑性在這方面的概念。
(2) Central Regulatory Mechanisms of Motor Coordination
There are several reasons for assuming that motor coordination, such as for gait, is regulated by a central controlling mechanism. Let us picture this mechanism as consisting, in its most primitive aspects, of spontaneous central nervous system activity, for example, a rhythmic beat related to metabolic processes within the brain (Lindsley, 1957). Lashley (1951) postulated such a central rhythmic activity to account for some of the phenomena discussed under the title of serial order. He conceived of the neural correlates for rapidly following movements as a kind of pacemaker activity, a source which emits spreading waves of facilitation alternating within inhibition, with the whole mechanism providing for a clock or timing device. (For elaborations see Chapters Three and Five.) Let us hypothesize, following the approach of P. Weiss and his students, that it is “nonplastic” because they are inherent in the most intimate organization of the brain, at least of higher organisms. In those animals where the central regulatory mechanism drives a great number of individual coordination patterns (movements used for grooming, pouncing, swimming, or nest-building activities), recombination of movements or partial patterns offers so many possibilities that a picture of nearly infinite variation is created. However, in animals where the central regulatory mechanism drives only a small repertoire of whole coordination patterns, recombination of partial movements is difficult to produce experimentally and, from a behavioral point of view, we are inclined to believe that the animal has a limited learning capacity. This is, in a few words, the hypothesis of this section.
(2) 中樞運動肌肉協調調節機制
許多推理假設運動肌肉協調如步伐，是由一種中樞控制機制所規範。讓我們將此機制最原始的一面想像成是由自然中樞神經系統活動組成。例如：有節奏的拍打和腦部變化的過程相關 (Lindsey, 1957)。Lashley (1951) 假設一個中樞韻律活動是依據一些討論連續程序的主題。他設想神經和快速接續的移動相關，如同一種節律器活動，一種發出簡易交替抑制的傳播震動，全機制備有時鐘或時間裝置的資源（更詳細的內容可參看第三章和第五章）。讓我們假設循著P.Weiss和他學生的方法，中樞機制或節奏活動和調節是『不可塑性的』，因為至少較高等生物體天生具有通達的大腦組織，而這些高等動物中樞調節機制可讓許多個別協調型態（一些用於打扮、猛撲、游泳、或築巢的肢體活動），活動重整或結合部分型態活動產生許多將進無限變化的可能性。然而，動物中樞調節機制只運作於整個調節型態的一小部分功能，重新排列部分的活動實驗上很難產生，從行為觀點來看，我們傾向於相信動物學習能力有限，以上為這部份簡略假設。
Since central regulatory mechanisms are referred to repeatedly throughout the book, a few more comments are in order. The argument is largely based on Lashley’s paper (1951), which should be consulted for fuller documentation and explanations.
由於這本書重複提到中樞調節機制，還有一些程序的評論，這些論點大多來自Lashley的論著，讀者可從他的作品中找到更多資料和解釋。
The smooth execution of any limb movement requires synergistic interaction of a considerable number of muscles. Most skeletal muscles are arranged into agonist-antagonist pairs. If one muscle contracts, the other has to relax or, more generally, an increase of tonus in its counterpart. If this reciprocity is interfered with by diseases such as Parkinsonism, tonic rigidity ensues. In the movement of a limb, an intricate timing mechanism comes into play in which the muscles of, for example, the shoulder-girdle, the humerus and forearm, of the hand, and of the fingers are activated in very rapid succession and with great precision. In addition to the timing mechanism regulating the muscular activities in a single limb, there must be coordinating mechanisms which relate the whole movement of one limb with that of all others, such as in the performance of forward or retrograde ambulation, of swimming, and scratching.
肢體運動平穩地執行需要相同數量肌肉的協同作用互動。大多數骨骼肌肉排列成促進-抗進配對，如果一邊肌肉收縮，則另一邊會舒張，更廣泛地增加一邊肌肉強直性，將伴隨減少另一邊肌肉強直性以達到協調。如果這種相互作用受到如帕金森氏症的疾病干擾，則會引起肌肉強直僵硬。分肢移動是由複雜時間安排過程和肌肉協同參與。例如：脊椎動作的胸帶、肱骨、前臂、手部和手指活動於非常快速和精確的接續動作。加上時間安排過程規範，每一分肢的肌肉活動，必須有和其他分肢相關的調節機制協同，如同游泳或抓、動作往前或往後。
The complexity of the regulatory mechanism may perhaps be made more illustrative if we compare it to a huge train-switching yard (that is, trains of nervous impulses!). Trains are dispatched according to schedules, one schedule for each motor pattern, each schedule calls for hundreds of simultaneous dispatches as well as a program of staggered dispatches where each successive train must start a fraction of a second after its predecessor.
At one time it was thought that the sequencing of muscular events was the product of a chain of associations; this belief is still widely held today. According to this theory, one motor event comes to be the stimulus for another motor event, these two now determining a third one, and so on. Lashley has shown that such chains of association cannot account for the sequential ordering of motor behavior. There are three major reasons for this: (1) motor events may occur in such rapid succession that there cannot sufficient time for impulses to be sent from stretch receptors in the muscle to the brain and then back to another muscle which is programmed to be the second in line to contrast; (2) certain rhythmic activities can be observed in many animals after far-reaching de-afferentation, that is, serving or blocking of the nerve fibers that carry information from the muscles to the center (v. Holst, 1934, 1937); (3) (this is the most important reason) an individual movement, using again flexion of a limb, is part of not just one but many different coordination patterns. Some animals, for instance, have three or hour different types of ambulation. In each type there are different sequences of foot-falls, and the limb as a whole may assume a different style of movement (whipping, slow-lifting, pushing, jerking, etc). But flexion at a given point is part of each of these various coordination patterns, even though the sequence of motor events us different for each type of gait.
If event A-B-C were simply chained by association, how could we account for the ease with which animals switch back and forth (and without apparent practice or learning) between this pattern and, for example, B-C-A or C-B-A? Chaining by association would let us expect considerably greater habit interference during switching of coordination patterns than is actually observed, Furthermore, it would lead us to expect that any sequence of muscular events could be arbitrarily chained together so that any new coordination pattern could be produced; this is not found to be actually true.
It is this type of argument supported by a wide variety of other biological phenomena that led Lashley to reject the chaining-by-association theory of serial ordering and to assume a different central regulatory mechanism. Instead of repeating the evidence by Lashley, let us turn once more to an analogy for illustration. Consider again the schedules for dispatching trains. The associative chain theory would hold that the movements of individual trains are the signals for movements of other trains. The central mechanism theory holds that neither individual trains nor their movements affect, by themselves, the movements of other trains following them in time. Instead it is the dispatch schedule that regulates the patterns of activities as a whole. Individual trains and their runs may be part of a variety of mutually independent schedules. According to the first theory, an engineer of a train B begins to move after he has seen train A arrive. But according to the second theory engineer B can make no use of the information from A since it may now be part of an entirely different schedule in which B does not follow A; it just await signals from central switchboard.
The logical argument offered by Lashley is supported by an impressive array of experimental findings. We have mentioned the experiments on salamander larvae in which limb buds were transplanted to inappropriate sites. If a left forelimb is amputated from a donor animal and transplanted as a supernumerary limb to a host animal where it is allowed to regenerate into the right armpit, the extra limb is soon found to be moving smoothly. No tonic rigidity is noticed, and therefore we must assume that agonist and antagonist muscles receive innervation that is appropriate to the muscle. Interestingly enough, the limb will move at the tome that is appropriate for a forelimb to move; since, however, we have changed sides in the process of transplantation, the super numerary limb will move in the opposite direction from the original limb that is next to it. Thus one limb cancels the effect of the other, and it is possible to have a preparation with totally paradoxical behavior.
What is the nature of this relationship between the limb and the brain? How can reciprocal innervation of muscles and timing of the limb with respect to other limbs be established in a fairly orderly way where there could not have been any neuronal “wiring” for the additional leg? Inspection under the microscope of the regenerated tissues does not reveal any visible order. Never fibers seem to have sprouted every which way, and the established connections seem to be entirely random. Could this be a delusion due perhaps to insufficient power of resolution of the light microscope? Is it possible that the nerve sprouts actually find their way to the appropriate muscle because of some unknown biochemical affinity between muscle and nerve? At first this possibility was never entertained. Instead it was thought that muscles were physiologically tuned to specific neuronal messages and simply responded whenever they “heard their name over the public address system.” This hypothesis was known as the muscle-resonance theory. However, Wiersma(1931) disproved the theory by recording electrical potentials from the nerves. Subsequently, the orderly recovery of motor coordination in the transplanted limb was interpreted on the basis of structural connections. There are two essential possibilities here. Either the nervous system entirely fixed and proper connections are made at the periphery in the way first mentioned, that is, fibers that carry given messages have the capacity of finding their way into the appropriate muscle during regeneration; or the muscles have the capacity of influencing the nerves that grow into them and thus affect the central nervous system retrogradely.
The first of these two possibilities has gained plausibility in most recent investigations (Mark, 1965) , although it is still far from established. The second possibility is favored by many of the neuroembryologists who had made the original discoveries on lower vertebrates. In Weiss’s own words (1950b) : It is thought now that “each muscle has a specific biochemical differential, that it projects this differential into the motor nerve fibers that come to innervate it and thus tunes (modulates) the motor ganglion cells to a specificity appropriate for the particular muscle. The ganglion cells have received their specificity by a retrograde influence (modulation) from the muscle itself.” Until recently, Sperry (1958) believed that the biochemical influence exerted by the muscle upon the nerve actually induces synaptic changes in the central nervous system. But Eccles et al. (1962) found only limited support for this interpretation, lending credence to Mark’s (1965) interpretation, a point of view that is also now favored by Sperry (1963). For an up-to-date review of the entire topic see Weiss (1965).
The importance of the original discovery is that in phylogenetically primitive vertebrates (and probably during fetal stages of most other vertebrates) there is an inescapable BaupIan (blueprint) for both the gross form and the sensory-motor integration. The surgical rearrangement experiments on lower forms show how difficult it is to interfere with the “preestablished harmony” of the movements of muscles throughout the body which accounts for smooth coordination.
Compare this situation with rearrangement experiments in mammals and adult forms of lower vertebrates. If the nerves which normally feed a flexor and extensor pair of muscles, respectively, are interchanged surgically and are allowed to regenerate into the wrong muscle, subsequent coordination becomes disordered and remains so.
The difference in the results of rearrangement between lower and higher forms is not as paradoxical as it might appear at first. Table 1.1 summarizes the situation for easier reference. We discern here the emergence of a specific theme. For all animals examined, rigid plans for development of form and motor coordination seem to exist. In primitive forms, tissues are less differentiated or specialized and thus participate in the organization responsible for motor coordination; end organs may influence the structure and function of centers as much as the centers may influence the periphery. The result is preservation of the original plan for integration. In adult and higher forms, tissues become more and more specialized and thus more independent of each other. The motor-integration plan is no longer “inscribed” in tissues other than those directly concerned with coordination, principally the brain. The basic plan or plans (the dispatch schedules) for sensory motor coordination are still as rigidly inherent in the internal organization of the animal but they are stored now in the central nervous system alone. In this context, the dimension of plasticity-rigidity refers exclusively to adaptation and readjustment of internal process, not to an animal’s adaptation to environmental conditions.
The situation for primates and man in particular is not completely clear. Although regeneration is also amyotypic and coordination is either permanently disarranged or at least always remains poor, some central nervous system mechanisms seem to have developed in those forms that enable the individual to make some secondary, partial readjustment. Perhaps this new learning is based on more complex cortical activities- possibly those that are experienced by man as will – but these speculations still lack empirical evidence.
The picture would not be complete without at least a superficial reference to the sensory disarrangement brought about by extracorporeal distortions, such as vision through wearing distorting lenses or prisms. Man, and a variety of lower forms, can learn quickly to make a number of adaptive corrections for these distortions (Kohler, 1951). However, the adjustment is not complete. In adjusting motor coordination to distorted visual input, it is essential that the individual goes through a period of motor adaptation, and there is cogent evidence that this is required for a physiological reintegration between afferent and efferent impulses and not simply to provide the subject with “knowledge” of the spatial configurations (Held and Hein, 1958), (Smith and Smith, 1962). Furthermore, man’s cognitive adjustment to visually distorted environment is never complete. Subjects who wear image-inverting goggles soon come to perceive the world right-side-up (through as the beginning it was seen upside down). But even after many weeks of relative adjustment, they experience paradoxical sights such as smoke from a pipe falling download instead of rising upward or snowflakes going up instead of coming down.
The over-all conclusion that must be drawn from the disarrangement experiments are first, that motor coordination (and certain behavior patterns dependent upon it) is driven by a rigid, unalterable cycle of neurophysiological events inherent in a species’ central nervous system; second, that larval, fetal, or embryonic tissues lack specialization; this enables these tissues to influence one another in such a way as to continue to play their originally assigned role despite certain arbitrary peripheral rearrangements. Because of this adaptability, species-specific motor coordination reappears again and again regardless of experimentally switched connections. Third, as tissues become more specialized- both in ontogeny and in phylogeny- the adaptability and mutual tissue influence disappears. Therefore, in higher vertebrates peripheral disarrangements cause permanent discoordination. Finally, with advance of phylogenic history, ancillary neurophysiological mechanisms appear which modify and at times obscure the central and inherent theme- the cyclic driving force at the root of simple motor coordination. More complex storage devices (memories) and inhibitory mechanisms are examples.
With the emergence of more specialized brains, the nature of behavior-specificity changes. Although it would be an inexcusable oversimplification to say that behavior, in general, becomes more or less specific with phylogenetic advance, there is perhaps some truth in the following generalizations. In the lower forms, there seems to be a greater latitude in what constitutes an effective stimulus, but there is a very narrow range of possible responses. Pattern perception, for instance, is poorly developed so that an extremely large array of stimulus configurations may serve to elicit a certain behavior sequence, and thus there is little specificity in stimulability. However, the motor responses are all highly predictable and are based on relatively simple neuromuscular correlates; thus there is high degree of response specificity. With advancing phylogeny, the reverse seems to become true. More complex pattern perception is correlated with greater stimulus specificity and has a wider range of possible motor responses, that is, less response specificity. However, both of these trends in decreasing and increasing specificity are actually related to greater and greater behavioral and ecological specialization. Taxonomists will be quick to point out countless exceptions to these rules. Evolution is not so simple and can never be brought to confirm to a few formulas. The statement here is merely to the effect that such trends exist and that, generally speaking, specificity both in stimulation and in responsiveness changes throughout the history of life.
In the vast majority of vertebrates, functional readjustment to anatomical rearrangement appears to be totally impossible. Even if the animal once “knew how” to pounce on prey, peripheral-central disarrangement will permanently incapacitate the animal from pursuing the necessities for its livelihood. If the primate order should indeed be proven to be an exception to this rule- and there is little evidence of this so far- then we would have to deal with phenomenon as an extreme specialization, whose details and consequences are yet to be investigated. There is such less modifiability for those coordination patterns which constitute species-specific behavior than is usually realized, and we must keep in mind that most behavioral traits have species-specific aspects.
This statement is not contradicted by the great variety of arbitrary behavior that is produced by training. Pressing a bar in a cage, pecking at a red spot, jumping into the air at the signal of a buzzer (in short, the infinity of arbitrary tricks an animal can be made to perform) do not imply that we could train individuals of one species (for example, common house cats) to adopt the identical motor behavior patterns of another, such as that of a dog. Although there is perfect homology of muscles, we cannot train a cat to wag its tail with a dog’s characteristic motor coordination. Nor can one induce a cat to vocalize on the same occasions a dog vocalizes instinctively, for instance, when someone walks through the backyard. Just as an individual of one species cannot transcend the limits to behavior set by its evolutionary inheritance, so it cannot make adjustments for certain organic aberrations, particularly those just discussed. The nearly infinite possibility of training and retraining is a sigh of the great freedom enjoyed by most mammals in combining and recombining individual traits, including sensory and motor aspects. The traits themselves come from a limited repertoire, are not modifiable, and are invariably species-specific in their precise motor coordination and general execution.
In Goethe’s words, addressing a developing being:
Nach dem Gesetz, wonach du angetreten.
So musst du seyn, dir kannst du nicht entfliehen,
So sagten schon Sibyllen, so Propheten;
Und jeine Zeit und keine Macht zerstűckelt
Georägte Form, die lebend sich entwichelt.*
*According to the law that summoned thee.
Thus must thou be, thy own thou canst not flee.
Thus spake the sibyls, thus the prophets:
And neither time nor might can deviate
Imprinted from alive developing.
Vocabulary
1. embryology n. 胚胎學
2. dichotomy n. 兩分;分裂;二分法;叉狀分枝;弦月
3. untenable adj. 難以防守的,不能防守的;(論據等)站不住腳的;不能租賃
4. evolutionary adj. 發展的;進化的;漸進的
5. Home-sapiens ph. 智人(現代人的學名)(h- s-)人類,人
6. divergence n. 分歧;背離;分離;相異
7. zoological adj. 動物學的;關於動物的
8. physiological adj. 生理的,生理上正常的
9. vertebrate n. 脊椎動物; a.有脊椎的;脊椎動物的
10. larval a. 幼蟲的;幼體的
11. salamander 【動】蠑螈;(傳說中生活在火中的)火蜥蜴,火蛇;火精,火怪;能耐高溫的物件;烤 板; 撥火棒;輕便烤箱
12. optic a. 眼的;視力的,視覺的
13. rotation n. 旋轉;【天】自轉
14. anatomic a. 解剖的;解剖學的
15. overgeneralization n. 過度類化
16. gait n. 步伐
17. metabolic a. 變化的;新陳代謝的
(Still updating)
FIG. 2.4. Lower facial muscles in man. Right: superficial layers; Left: deep layers. (From Brausm 1954.)
