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displayed in the actions or functions of living bodies, and hence it has been defined "The Science of Life." For illustration, let us take the lungs we examine their investing membrane (the pleura), their lobes and lobules, their air cells, the windpipe branching through them, their arteries, veins, absorbents, and nerves, their situation in the thorax, their colour at different ages, their connexions, their relations to the diaphragm, ribs, &c. and any other circumstances connected with their structure— that is Anatomy. But the lungs are the great organs of respiration; whatever, therefore, relates to their inhalation and exhalation of air, the changes which such air undergoes in breathing, the alterations effected by its presence on the blood contained in the pulmonary blood-vessels, and all such other points as relate to the function of the lungs, are included under the head of Physiology; and so it is with the functions of other organs. You will recollect, then, that whatever relates to the structure of any organ, belongs to Anatomy, and whatever relates to the vital phenomena displayed by such organs, or, in other words, to the actions or functions it performs in the animal economy, belongs to Physiology.

ANATOMICAL TERMS.

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It is to be observed, however, that while Anatomy and Physiology are thus defined as separate and distinct branches of science, yet, so intimate is their connexion, that neither can be fairly understood without the other. Physiology can never be comprehended without a previous knowledge of Anatomy; and the latter, when isolated from the former, loses half its value.

You will now attend to the following terms:1. Human Anatomy (Anthropotomy) relates, of course, to the structure of man alone.

2. Comparative Anatomy (Zootomy), to that of other animals compared with man.

3. Morbid or Pathological Anatomy, relates to those changes in structure which are caused by disease.

4. Vegetable Anatomy (Phytotomy).

5. Vegetable Physiology contemplates the vital phenomena of plants; for you must recollect, that although the latter are neither possessed of locomotion, sensation, nor perception, still they are living bodies; of which innumerable proofs might be advanced if necessary: and as you have not, probably, directed your attention to this subject, I will make a few remarks upon it.

Have you ever observed the different appearance which a field of clover presents on a fine sunny day, and on one which is bleak and lowering? In the first case, the leaves are all expanded and spreading their upper surface to the light; in the second, they are shrunk up or closed, their leaflets being bent down to elude the chilling influence of the air and moisture. In numerous other plants you will find a similar sensibility: observe, for instance, the common daisy after sunset or in wet weather, and you will remark that the flower is no longer expanded, but that the petals or flower-leaves of its ray or border are raised up, their tips being in contact, and forming a canopy over the disk, or central part, to defend it from the rain or dew.

Here, then, are two very familiar examples of sensitiveness to the states of the weather, and which can only be referred to the life or vitality of the species mentioned. But much more remarkable examples may be adduced of vegetable life from some plants which possess higher degrees of irritability, and a contractility of fibre apparently analogous to that of an animal muscle. Thus the appendage attached to the extremity of the leaf of the Dionœa muscipula

VEGETABLE IRRITABILITY.

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(Venus's Catchfly), is so curiously constructed, and is endowed with so high a degree of irritability, that the moment the latter is excited by the touch of an insect, the appendage suddenly closes, and crushes the animal in manner of a spring rat-trap.

The leaves, again, of the moving plant Hedgsarum gyrans, a native of India, are in almost constant motion, revolving on their footstalks from side to side. A stamen of the Barberry, when touched on the inside of the filament near its base, strikes the anther against the stigma with violence, as if it had been let loose from a spring; while in the sensitive plant, and some other mimosa, the phenomena displayed in the successsive closures of the winged leaves, and bending down of their footstalks, when only one portion of the plant has been touched, are still more remarkable and simulative of animal life.

The rise of the sap in plants, their dependance on air for respiration, the formation of innumerable substances by the action of their vessels, as oils, resins, sugars, gums, odours, poisons, &c. &c. their sexual distinctions, their germination and propagation of their species, their intolerance of temperatures not suited to

their individual constitutions, their being killed like animals by arsenic and other poisons, with endless other phenomena exhibited in their history, might be adduced in proof of their vitality; and hence you will perceive, that the term Physiology is as legitimately applied to their functions, as to those which characterize animal life.

All organic bodies, then, that is to say, all animals and plants, are possessed of life, which no inorganic body is. A stone does not live; it has not organs for receiving nutriment, and others for converting such into its own substance; it has no vessels for circulating fluids, no organs for elaborating various secretions; it has not sprung from parents; does not grow from infancy to maturity, and produce other bodies like itself; and, as it has never lived, it cannot go through the process of dying, as all animals and plants do: and the same facts apply to all other inorganic bodies whatever, and to organized bodies also, after their vital spirit has become extinct.

But, while all the individuals belonging to the animal and vegetable kingdoms possess life, it must be easily apparent that there are mighty differences in the vitality enjoyed by

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