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Lesson on the Blood.

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are your brethren, you are responsible to God for their characters. Will your denial that it is so, in the great day of accounts, avail you any thing? Will you dare to say to the Judge of all, Am I my brother's keeper ?

l'RACTICAL LESSONS ON PHYSIOLOGY.

LESSON II.-THE BLOOD.

In a former lesson, I have told you something about the circulation of the blood. I have spoken of the manner in which it circulates, the rapidity of its circulation, the machinery concerned, and the quantity of this fluid which a healthy adult body usually contains.-I now propose to tell you what sort of a fluid the blood is.

I have told you that there is something like a pail full of blood in the healthy body of an adult, and that it is contained or held in vessels, which like little rivers have their numerous small ends, (like our springs and rivulets, in relation to the world we inhabit) in the limbs and remote parts of the system, inside and outside; and are connected by their larger ends with the heart in the centre. Now as the water is constantly running into the sea, and finding its way back again through the clouds and otherwise, to the fountains and springs, to run into the sea again, so the blood is constantly running into the heart, and yet as constantly finding its way back to the extremities, to run back again into the heart, and thus coursing its way through the system, every three or four minutes.

There is at least, one striking difference, however, between the rivers of water in the world we occupy, and the rivers of blood in that miniature world which the human soul lives in. Water cannot be said to have life, or to be subject to diseases. it may indeed become stagnant, or by the admixture of poisonous substances produce disease ; but it is not true to speak of its being subject to disease in the same way with the blood. And as for being alive, it is no more alive than the earth-clay, marl, lime or gravel-on which it runs. But the blood, no less than the soil through which it runs, is truly and essentially alive, i. e., it has vitality or vital properties.

This doctrine that the blood has life or vitality is indeed an old doctrine ; but not therefore the less true. It is as old at least as Ncah ; in whose days it was said ; • Flesh, wbich is the life thereof which is the blood thereof, ye shall not eat.' Moses too, who understood Physiology pretty well, says, both in Levit

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Character of the Blood. icus and Deuteronomy, that the blood is the life,' or the life of the flesh.'

The whole of the blood when it has just been changed by air, 'in the lungs, and is about to be sent out into all parts of the body through the arteries, is of a rich scarlet or vermilion color. As it goes out into the smaller arteries, the color grows somewhat deeper, till it finds its way into the small veins, where it is purple. As it runs along back in the veins towards the heart, it becomes of a deep purple, and finally almost black. It is, in this dark state, carried again to the heart, and its color is changed.

The heat of the blood is about 980 of Fahrenheit. It is, however, a little warmer-a degree or two –in the heart and great arteries, just after it has come from the Jungs, to be sent round the body, than it is after it has run its course, and got back again. Whether the weather is cold or hot, the heat of the blood, if we are in health, is about the same.

Blood, on being taken out of the living body and suffered to cool in a gradual and natural manner, separates into two parts. One of these is in the form of clots, and is called, in books, the crassamentum ; the other is a yellowish watery liquid, called serum. If any of you have ever had a friend bled in the arm, and have seen the blood after it had been kept in the bowl a few hours, you have probably observed the change. The crassamentum consists of a stringy or fibrous substance, of a lightish color, and little round red particles, called globules, entangled, as it were, in it; just as small substances might become entangled in a skein of thread or yarn. The seruin is chiefly water; nevertheless, it has in it, in a dissolved state, a small amount of many kinds of salts, and among the rest a little iron. Dr Good says the blood of about forty men contains iron enough to make a ploughshare.

I have said that there are little red globules, entangled in the fibrine, to form the crassamentum. While the blood is in the body and retains its vitality or life, these red globules swim in in it, and though extremely small, are yet so numerous and so deep colored as to give the blood its red appearance. Their color seems to reside in a small skin or pellicle which covers the globule. Here are the pictures of these globales. They are

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Further Illustrations of the Blood.

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magnified as they appear here, 400 times ; that is, they are 400 times larger in diameter than in their natural state in the blood. The first cut, or d, represents the globule with its coat or pellicle still on it; while e represents it with the pellicle taken off.

You will think these red globules of the blood very small, to be only a four hundredth part as large in diameter, as the spots in the picture; and they are so. If they could be laid closely together, in a row, it is thought by naturalists that it would take no less than 1940 of them to form a row an inch long; and a hollow ball an inch in diameter would hold 7,301,384,000 of them.

The use of these red globules in the blood, that is, the reason why the blood is better for having them in it, or especially for being red rather than some other color, is not well known.

The fibrine or thready substance, in which the red globules are entangled, when the blood cools and coagulates, or dies, is the most important pari of the blood. From this, all the various parts of the body are formed. How they form the parts of the body is conjectural. We only know the fact.

Some suppose that the fibrine of the blood is made from the globules. They think that these, in swimming round, as it were, in the blood, at last attach themselves together by some known or unknown law, and form the fibrine. Those who believe in this doctrine suppose the red globules come together and arrange therselves in a mass to form a row, as in the following engraving; and that this row becomes a fibre:

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I have one more picture to show you. You have been al. ready told that all the various parts of the body are made from the fibrine of the blood. This fact is most obvious in the formation of muscle, or what is usually called lean flesh. This lean flesh, or muscle, is made of threads or fibres, and these fibres also seem to be divisible again into hibres, smaller still. But when we come to the smallest fibre we can find it is thought to be made up in the manner already mentioned ; that is, of little particles or red globules of blood, joined together, as represented on the following page.

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But I must stop here, not because there is nothing more to say on the subject, but because I have no time nor space for it. In my next lesson I shall endeavor to tell you how blood is formed, and describe to you the curious and coinplicated apparatus which is concerned in forming it.

SCHOOL REGISTERS.

The Massachusetts Board of Education have published a blank register for the use of schools which, if faithfully kept by teachers generally, must furnish the Board with a thorough history of the schools annually. The register is to contain the names of the teacher and committee, with the number and names of the scholars in the several schools, male and female ; their ages ; time of entering and leaving; the names of their patents or guardians; their daily attendance and absence, forenoon and afternoon; the whole number of days' attendance ; present or absent at each visitation of school committee; the names of books; every study which cach scholar pursues ; deficiency of class books; days when visited by school comınittee ; names of committee present; time of commencing and ending the school, with remarks.

To convey some idea of the particularity of the requisitions of this register, says the Traveller,' (from which we copy the fore. going, not having a copy of the School Register at this moment before us,) the teacher is required, for each attendance or ab

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sence in the forenoon, to make a cross or a dash in the upper left hand corner of a square one tenth of an inch in width, and for the same in the afternoon, to make a simple sign in the lower right hand corner of the same square.'

The editor of the Traveller thinks the foregoing quite too much for a teacher to perform, without neglecting his other duties. He is especially displeased with the minuteness or particularity required, and attempts to throw ridicule on it, by talking about the demand for 'magnifying glasses,' and 'humming bird's quills.' Have those newspaper editors, who are so ready to pass judgment on every subject which comes up, whether they understand it or not-have they, we say, any practical knowledge of school keeping? Do they indeed know any thing of the reasons which exist for having a register kept? Do they know how much space there is for writing on a spot a tenth of an inch square? Surely there is room enough for two small dashes or marks. We believe it would not be out of the way to say that all the really important events of many a man's life might be written out on this little spot of a tenth of an inch square.

The experience of many years teaching convinces us that every school ought to have a register of at least equal minuteness, with that recommended by our board. It has a prodigious effect not only on the school, but on the teacher himself; and it will do much to elevate the character of both.

DUTIES OF SCHOOL EXAMINERS.

Great efforts are making in many parts of the United States, at the present time, to raise, in various ways, the character of Common Schools and Conmon School Education. Among the efforts which have particularly interested us, have been the proceedings of the Board of Examination of Common Schools for Cuyaboga County, Ohio. This Board, at a meeting held in Cleveland in May last, and in conformity with the new School Law, adopted a code of by-laws embracing the following arrangements in the appointment of Special Examiners.

To facilitate the future examination of teachers, they first divided the County of Cuyahoga into five districts, each district, except the first, containing four townships. Of the first dis:rict, consisting of Cleveland and two other townships, the County Board of Examiners are to be the Special Examiners, but the

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