23G 



♦ KNOWLEDGE ♦ 



[April 20, 1833. 



"OUR BODIES:" 



SHORT PArEllS ON PHYSIOLOGY. 



By Dk. A.vi>i:k\v \\'ii.son, F.R.S.E., ic. 



yo. X.— THE BLOOD. 



'lltTJlF-N* tho voice of ancient authority declared the 

 V* blood of the body to be its "life," the statement 

 was one which the experience of everyday life seemed fully 

 to support. The phy.siologist of to-day will not quarrel 

 seriously with the ancient rendering. He knows the 

 impossibility of defining this mystic " life " of ours, which 

 appears now as diversity in unity, and then as unity 

 amidst variety of the mo.st complex kind. Ho also knows 

 'that many other parts or components of the body might 

 with e(iual justice be named the "life" — at least, in the 

 sense in which the blood has been so termed. The top of 

 the spina! cord (or mediilla oblongata, as this part of the 

 nervous axis has been named) might, perhaps, with greater 

 force than the blood, be named the "life," since we can 

 lose a pint or two of blood and recover perfectly from the 

 depletion, whilst a prick with a pin in the medulla would 

 cause instant death. Similarly, the lieart might quite 

 appropriately be named the " life," in the sense of the 

 absolute necessity of its action for the continuance of the 

 .-iirculation. The " breath," also, is the "life" in a very 

 iplain and unmistakable sense, since interference with the 



■ "-isreatlnDg function means primarily death to the blood 

 ■itself. But when we consider that the blood-flow is 



■ incessant, that it travels to all parts of the body, and that 

 its failure means deprivation of food to the tissues, as well 

 as the want of heat-production, we can readily enough find 

 ample justification for the words of ancient wisdom with 

 ■which we opened this paper. 



What is blood ? An important question this, and one 

 •which may be answered in at least three ways — firstly, 

 physically ; secondh', chr micall ij ; and thirdly, micro- 

 ■smpicaUij. Let us, firstly, endeavour to ascertain the 

 •physical characters of blood, or those which blood exhibits 

 when regarded merely as a particular kind of fluid. To 

 the naked eye, blood appears of a bright red colour as it 

 Mows in tlie arteries — that is, when it is pure ; whilst it is 

 of a purple colour when, in an impure state, it circulates 

 through the veins. iSIicroscopioally, as we shall presently 

 see, blood is not really red in hue, Vmt owes its colour to 

 the numerous red bodies (or corpuscles) which float in it. 

 Blood is feel)ly alkaline in its reaction, and this alkaline 

 character decreases from the time of the remo\ al of the 

 blood from the body, and until it clots or " coagulates." 



When drawn from the body, blood "clots." From two 

 to five or six minutes suflioe for this action. At first, the 

 blood appears as a red jelly ; but, ultimately, the clot sinks 

 to the bottom of the vessel, leaving a straw-coloured liquid 

 above. Blood thus practically analy.ses itself before our 

 • eyes, into a solid part, the clot, and a liquid part, the 

 ■£crum or plasma. The clot consists of the corpuscles or 

 globules of the blood (most of them red, hence the character 

 of the clot) entangled in a substance called Jil/riu. The 

 liquid, or plasma, is the normal liquid or fluid part of the 

 blood itself. Tliis fluid, the microscope shows us, is as 

 clear as water, and owes its apparently red colour, as 

 already remarked, to the red globules that float in it. It 

 is owing to a few of these red corpuscles remaining sus- 

 pended in the plasma, that the liiiuid part of the blood in 

 the " clot" seems to be straw-coloured. If we whip up or 

 switch the blood with a bundle of twigs, just after it has 

 tieen shed, no clotting t;xkes place. In such a case, we 

 ivhip out from the blood the fibrin which entangles the red 



corpuscles, and which adheres in strings or shreds to the 

 twigs. 



The chemical composition of the blood may be very 

 shortly dealt with. A fluid which is supplied to every 

 part of the body, and from which each organ or tissue 

 derives the materials wherewith to renovate and repair its 

 substance, might reasonably enough be e.xpected to pre- 

 sent us with a fluid epitome of the entire frame. And 

 so, in truth, do we find blood to exhibit a composi- 

 tion of wide and generalised character. We discover, for 

 instance, that blood contains about 784 parts of water per 

 1,000; it is vicli in albumen ; it contains /at I >/ matters; it 

 has a complex list of minerals, such as common salt, 

 chloride of potass, phosphates of lime and magnesium, 

 carbonate of sodium, itc. ; and it shows on analysis, 

 colouring matter, gases, and a number of substances de- 

 ri\ed from the waste of the Ijody. Another fashion of 

 showing the chemical composition of blood, brings out its 

 elementary constitution as follows: — Carbon, 57'9 ; 

 hydrogen, 7-1 ; nitrogen, 17'4; oxygen, 19'2 ; ashes, 4'4. 

 From such an estimate, we see that blood contains 

 materials adajited for supplying all the tissues of the 

 body in the reparative work which is incessantly being 

 performed. 



Under the microscope, a thin film of human blood is seen 

 to consist of a clear liquid — the plasma — in which float 

 two kinds of bodies. These are the red and vhite corpuscles, 

 or " globules," as they are often popularly named. The 

 blood derives its red colour from the immense number of 

 red corpuscles which float in its liquid. The white globules 

 are less numerous ; about one white corpuscle existing to 

 400 or 500 red ones. The microscope enables us to see in 

 between the globules, aiid thus to perceive the clear liquid. 

 To the naked eye, conversely, the blood Appears uniformly 

 red, because the globules are so numerous, and because we 

 cannot perceive the liquid in which they float. Each red 

 corpuscle of man measures in breadth about -g^'goth of 

 an inch, and in thickness about yu-J-Tj^th of an inch. 

 In shape it is biconcave, or hollowed on either side, and is 

 coloured red by a substance called hoimoglohin. It is this 

 substance which is affected by the oxijgen we breathe into 

 the blood, and by the carbonic acid gas the body and 

 tissues at large excrete into the blood. The white corpus- 

 cles of man's blood measure in diameter, each, about the 

 ->;\,-jyth of an inch. Each contains a central particle, the 

 nucleus. It appears to be this nucleus which, when libe- 

 rated from the outer part of the white corpuscle and 

 coloured red, becomes a red corpuscle. The red corpuscles 

 of the blood arc thus derived from the white ones. 



The white corpuscles of the blood are known to possess 

 the curious property of exhibiting movements similar to 

 those seen in the «?;«), 6«-animalcule. These corpuscles 

 (like the amceb<() can also absorb particles of solid matter, 

 as the animalcule in question takes its food. The white 

 corpuscle is, therefore, a particle of living protoplasm, pos- 

 sessing a vitality independent, in a measure at least, of 

 that seen in the body of which it forms part. It is, indeed, 

 a curious fact to ponder over, that rolling about in our 

 veins and arteries ; now worming their way through the 

 walls of blood-vessels into our tissues, and now contracting 

 and expanding their substance, are myriads of minute 

 living specks, which, although part and parcel of our com- 

 position, are closely related in structure and life to the 

 animalcules of the pool. 



SpAN'isii Iron Miner.\ls. — The exports of iron minerals 

 from Spain during the year 1880 amounted to 2,932,998 

 tons. 



