In reality, however, all the organs are double. The reason for this is that the body itself is double, consisting of two halves, which are however combined together under one supreme1 centre. For there is an upper and a lower half, a front and a rear, a right side and a left.
This explains why it is that even the brain and the several organs of sense tend in all animals to consist of two parts; and the same explanation applies to the heart with its cavities. The lung again in Ovipara is divided to such an extent that these animals look as though they had actually two lungs. As to the kidneys, no one can overlook their double character. But when we come to the liver and the spleen, any one might fairly be in doubt. The reason of this is, that, in animals that necessarily have a spleen, this organ is such that it might be taken for a kind of bastard2 liver; while in those in which a spleen is not an actual necessity but is merely present, as it were, by way of token, in an extremely minute form, the liver plainly consists of two parts; of which the larger tends to lie on the right side and the smaller on the left. Not but what there are some even of the Ovipara in which this condition is comparatively indistinctly marked; while, on the other hand, there are some Vivipara in which the liver is manifestly divided into two parts. Examples of such division are furnished by the hares of certain regions, which have the appearance of having two livers, and by the cartilaginous and some other fishes.
It is the position of the liver on the right side of the body that is the main cause for the formation of the spleen; the existence of which thus becomes to a certain extent a matter of necessity in all animals, though not of very stringent3 necessity.
The reason, then, why the viscera are bilateral4 is, as we have said, that there are two sides to the body, a right and a left. For each of these sides aims at similarity with the other, and so likewise do their several viscera; and as the sides, though dual5, are knit together into unity6, so also do the viscera tend to be bilateral and yet one by unity of constitution.
Those viscera which lie below the diaphragm exist one and all on account of the blood-vessels8; serving as a bond, by which these vessels, while floating freely, are yet held in connexion with the body. For the vessels give off branches which run to the body through the outstretched structures, like so many anchorlines thrown out from a ship. The great vessel7 sends such branches to the liver and the spleen; and these viscera-the liver and spleen on either side with the kidneys behind-attach the great vessel to the body with the firmness of nails. The aorta9 sends similar branches to each kidney, but none to the liver or spleen.
These viscera, then, contribute in this manner to the compactness of the animal body. The liver and spleen assist, moreover, in the concoction10 of the food; for both are of a hot character, owing to the blood which they contain. The kidneys, on the other hand, take part in the separation of the excretion which flows into the bladder.
The heart then and the liver are essential constituents11 of every animal; the liver that it may effect concoction, the heart that it may lodge12 the central source of heat. For some part or other there must be which, like a hearth13, shall hold the kindling14 fire; and this part must be well protected, seeing that it is, as it were, the citadel15 of the body.
All sanguineous animals, then, need these two parts; and this explains why these two viscera, and these two alone, are invariably found in them all. In such of them, however, as breathe, there is also as invariably a third, namely the lung. The spleen, on the other hand, is not invariably present; and, in those animals that have it, is only present of necessity in the same sense as the excretions of the belly16 and of the bladder are necessary, in the sense, that is, of being an inevitable17 concomitant. Therefore it is that in some animals the spleen is but scantily18 developed as regards size. This, for instance, is the case in such feathered animals as have a hot stomach. Such are the pigeon, the hawk19, and the kite. It is the case also in oviparous quadrupeds, where the spleen is excessively minute, and in many of the scaly20 fishes. These same animals are also without a bladder, because the loose texture21 of their flesh allows the residual22 fluid to pass through and to be applied23 to the formation of feathers and scales. For the spleen attracts the residual humours from the stomach, and owing to its bloodlike character is enabled to assist in their concoction. Should, however, this residual fluid be too abundant, or the heat of the spleen be too scanty24, the body becomes sickly from over-repletion with nutriment. Often, too, when the spleen is affected25 by disease, the belly becomes hard owing to the reflux into it of the fluid; just as happens to those who form too much urine, for they also are liable to a similar diversion of the fluids into the belly. But in those animals that have but little superfluous26 fluid to excrete, such as birds and fishes, the spleen is never large, and in some exists no more than by way of token. So also in the oviparous quadrupeds it is small, compact, and like a kidney. For their lung is spongy, and they drink but little, and such superfluous fluid as they have is applied to the growth of the body and the formation of scaly plates, just as in birds it is applied to the formation of feathers.
On the other hand, in such animals as have a bladder, and whose lung contains blood, the spleen is watery27, both for the reason already mentioned, and also because the left side of the body is more watery and colder than the right. For each of two contraries has been so placed as to go together with that which is akin28 to it in another pair of contraries. Thus right and left, hot and cold, are pairs of contraries; and right is conjoined with hot, after the manner described, and left with cold.
The kidneys when they are present exist not of actual necessity, but as matters of greater finish and perfection. For by their special character they are suited to serve in the excretion of the fluid which collects in the bladder. In animals therefore where this fluid is very abundantly formed, their presence enables the bladder to perform its proper office with greater perfection.
Since then both kidneys and bladder exist in animals for one and the same function, we must next treat of the bladder, though in so doing we disregard the due order of succession in which the parts should be enumerated29. For not a word has yet been said of the midriff, which is one of the parts that environ the viscera and therefore has to be considered with them.
点击收听单词发音
1 supreme | |
adj.极度的,最重要的;至高的,最高的 | |
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2 bastard | |
n.坏蛋,混蛋;私生子 | |
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3 stringent | |
adj.严厉的;令人信服的;银根紧的 | |
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4 bilateral | |
adj.双方的,两边的,两侧的 | |
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5 dual | |
adj.双的;二重的,二元的 | |
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6 unity | |
n.团结,联合,统一;和睦,协调 | |
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7 vessel | |
n.船舶;容器,器皿;管,导管,血管 | |
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8 vessels | |
n.血管( vessel的名词复数 );船;容器;(具有特殊品质或接受特殊品质的)人 | |
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9 aorta | |
n.主动脉 | |
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10 concoction | |
n.调配(物);谎言 | |
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11 constituents | |
n.选民( constituent的名词复数 );成分;构成部分;要素 | |
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12 lodge | |
v.临时住宿,寄宿,寄存,容纳;n.传达室,小旅馆 | |
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13 hearth | |
n.壁炉炉床,壁炉地面 | |
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14 kindling | |
n. 点火, 可燃物 动词kindle的现在分词形式 | |
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15 citadel | |
n.城堡;堡垒;避难所 | |
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16 belly | |
n.肚子,腹部;(像肚子一样)鼓起的部分,膛 | |
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17 inevitable | |
adj.不可避免的,必然发生的 | |
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18 scantily | |
adv.缺乏地;不充足地;吝啬地;狭窄地 | |
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19 hawk | |
n.鹰,骗子;鹰派成员 | |
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20 scaly | |
adj.鱼鳞状的;干燥粗糙的 | |
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21 texture | |
n.(织物)质地;(材料)构造;结构;肌理 | |
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22 residual | |
adj.复播复映追加时间;存留下来的,剩余的 | |
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23 applied | |
adj.应用的;v.应用,适用 | |
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24 scanty | |
adj.缺乏的,仅有的,节省的,狭小的,不够的 | |
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25 affected | |
adj.不自然的,假装的 | |
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26 superfluous | |
adj.过多的,过剩的,多余的 | |
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27 watery | |
adj.有水的,水汪汪的;湿的,湿润的 | |
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28 akin | |
adj.同族的,类似的 | |
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29 enumerated | |
v.列举,枚举,数( enumerate的过去式和过去分词 ) | |
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