Perhaps not very much more is effected when the further statement is added that, in a single human body, there are six thousand times as many of these microscopic blood-corpuscles as there are living human creatures inhabiting the world. Allowing fifteen pounds of blood for the quantity contained in the body of a man of fair stature, and reckoning that of this blood oneseventh part, or two pounds and two ounces, is made up of corpuscles, and that there are seventy thousand millions of corpuscles in each cubic inch of the two pounds and two ounces, the sum total for the whole array of corpuscles comes out nearly two and a half millions of millions. It is to be feared that the only notion that can be realised from this computation is the very inadequate and crude one, that the minuteness and number of these most wonderful little objects are far beyond all clear apprehension.

The individual corpuscles of the blood are just visible, as exquisitely minute rings, when looked at through a good microscopic object-glass of one inch focus, which magnifies forty diameters. With an eighth of an inch object-glass, used with an eye-power that qualifies it for magnifying 1,200 diameters, each corpuscle appears as if nearly half an inch wide. The most expert histologists now accomplish even more than this, and successfully employ in their examination microscopic powers that magnify even 2,800 diameters.

When the circulating blood is observed in the small vessels of the web of the frog's foot, it is seen that the coloured corpuscles are hurried on in a thickly serried phalanx in the clear stream which flows through the channel of each little vessel, with a tendency to crowd themselves up into the middle of the passage as much as they can. The colourless corpuscles are observed for the most part loitering along in the outskirts of the stream, often in actual contact with the sides of the vessel, and on that account advancing in the current with less resolute and impetuous pace. Under ordinary circumstances there are but few colourless corpuscles in comparison with the coloured ones-not more than a single one to every two or three hundred. To cursory observation the colourless corpuscle looks like a translucent ball, knobbed over by bosslike projections, and rolling over and over as it moves. More exact and careful scrutiny, however, shows that the little sphere is incessantly changing its form-protruding now one part and now another of its outer surface, and twisting and contorting itself into all sorts of indescribable shapes. The entire substance, indeed, of which the corpuscle is made is in perpetual unsettlement, flowing and rolling about in all conceivable

directions. By some trained and competent observers the corpuscle is described as insinuating itself into and through the finest slits and pores, by first pushing forward the minutest perceivable finger or feeler of its substance into the available chink, and then bringing after the feeler all the rest of the corpuscular mass in the same attenuated way, until the opening is passed, when the corpuscle forthwith expands to its larger dimensions in the less restricted space beyond. This power of insinuating itself into the narrower openings and cavities by its own inherent movement and moulding of its shape very remarkable. Very commonly, when specks of superior activity and increased condensation are seen to appear here and there in the mass of the corpuscle, it augments in size, and finally splits asunder into fragments; thus creating a brood of young corpuscles, each endowed with the same power of inherent activity and growth.

is

There is no shadow of doubt that the pale corpuscle of the blood is formed out of the fully prepared and most finished albuminous material; that it is, so to speak, the consummation of the first act of vital organisation. It is, in fact, a living creature fashioned, in some way or other, out of the richly elaborated material of the liquid in which it appears. In the colourless corpuscle life is contemplated in its most rudimentary condition; it is life seen at its dawn.

The most striking, and, on the whole, most characteristic peculiarity of this remarkable body, which distinguishes it from the unvitalised plastic matter that lies around, and that has been so immediately and so intimately concerned in its formation-the great stamp, as it were, of the new-born vitality with which the constituent material has become endowed-is its marvellous inherent power of spontaneous motion. The constituent spherules and molecules of which its mass is built up are, not firmly compacted together, but incessantly dancing hither and thither, and rolling over and over among themselves.

A second stamp-mark of the vital condition, which for the first time appears in the colourless corpuscle, is individual enlargement, or growth. The living corpuscle increases its own substance out of the molecular contributions which it receives from the surrounding nutrient material.

A third distinctive mark of the living state is that the substance of the life-endowed corpuscle has the power of constructing a peculiarly complex material which is no longer alive, although it has been so directly produced by living operation, and which furthermore is quite unproducible in any other way. This is what is known technically as formed

'substance.' There is not unreasonable ground for the notion which is entertained by some physiologists, that the highly plastic fibrin of the blood is itself formed substance' of this character, which has been made by the elaborating energy of the corpuscles.

By these various observations and considerations physiologists arrive at the conclusion that there are three altogether distinct states of complex material with which they have to deal in considering the first steps of vital organisation:-1st. that which is known as food-substance, or formative material. 2nd. living substance-formative material, which has been endowed with absolute vitality. And, 3rd. formed substance, the final result of vital operation, not itself alive, but which has been formed by the process of living elaboration, and which can only be formed in that way. Formative material and living substance are seen respectively in the albuminous principle and in the corpuscles of the blood. More particular allusion will have to be made presently to the formed material. In the meantime it should be understood that the most intelligent modern physiologists seem to be pretty well satisfied that it is a fundamental law of living economy that 'formative material' must pass through the ordeal of becoming itself living substance' before it can by any possibility be 'formed substance;' and that this virtually is the reason why the formed substance' of organised structures cannot be produced by any unliving agency. Hence, also, all the three distinct states of organic material are of necessity present in living bodies. For some time the actual living substance of an organised structure was spoken of as its 'protoplasm,' or first organised base. The more expressive and more philosophic term, Bioplasm' (Life Plasm, or Living Plasm), has now been accepted, in its stead.

Exquisitely and almost inconceivably small as these living corpuscles of the blood are found to be, in comparison with the grosser objects that form the unmicroscopic' sphere of ordinary observation, they are nevertheless, it must be remembered, themselves gross masses, if they, in their turn, are compared with the literally immeasurable masslets which are used in their fabrication. Each separate corpuscle is, itself, individually made up of parts, or particles, that can just be discerned under the highest powers of the microscope performing the peculiar vital movements that have been described; and these parts, or particles, are themselves made of yet other constituent parts also unquestionably of complex constitution; that is, of material which has had, at least, several different kinds of elemen

tary substance brought together to accomplish its formation. Indeed, it may be unreservedly stated, as an axiom of physiological science, that the ultimate spherules, or molecules, of which food-substance is composed, and of which living texture is built, are so very small that they are removed quite beyond the sphere of visibility, even when this is extended to its utmost range by the greatest powers of the microscope. The material substance in which the special changes are brought about that convert dead matter into living matter cannot be seen by human eyes. They occur in a region of material existence that is altogether beyond the reach of the visual powers which have been accorded to man. They cannot, therefore, be made the object of the direct observation of human philosophers. This, no doubt, is one reason why human intelligence has failed hitherto to unveil this particular mystery, and to demonstrate what life is.

6

The formed substance' made by the agency of living bio'plasm' is necessarily placed, in the first instance, immediately outside of the vital and generating mass; it is thrown off, so to speak, to its outer surface. In the case of small isolated aggregations of living substance, such as are the blood-corpuscles now under consideration, the substance, thus generated and thrown back to the outer surface of the corpuscle, may be scattered at once into the general current of the blood, as most probably happens with the great part of the fibrin that is thus fabricated. But, in other instances, the formed substance is retained around the aggregation of bioplasm and condensed into a kind of investing film. In other words, the little living body encloses itself in an outer coat of its own making; and so becomes what is termed, in physiological language, a vesicle,' or 'cell.' When the outer case, or cell-wall, of formed substance has once been framed in this way, all further supply of formative food for the interior living mass is drawn in through the actual substance of the investing film, being filtered through its invisible and almost inappreciable pores. The imbibed food is appropriated, in the first instance, to the enlargement and renewal of the aggregation of living molecules within the cell, and then to the construction of further additions of formed substance, which are returned to the outer surface of the living corpuscle, and are there plastered round the interior of the cell-wall, thickening and strengthening it, and otherwise changing and modifying its character. All the various textures of the living animal body-bone, cartilage, membrane, flesh, and brain -are, indeed, constructed in this way. Whenever such a proceeding is requisite, a considerable number of the com

pleted vesicles are fitted and fixed together to fabricate continuous texture, and the fabricated mass is then permeated by delicate channels and tubes so contrived as to enable them to bring in fresh supplies of the nourishment that is still needed for the support and perfection of the vesicles. As the development of the building-up vesicle proceeds the living internal germ becomes continually less and less, and so dwindles away, while the outer-formed investment becomes thicker and more pronounced in its structural character, until at length the living germ disappears altogether, and a formed, but no longer living, cell' remains as the final result of the operation. Cells, or vesicles, are so commonly formed under the constructive energy of corpuscular aggregations of bioplasm, that for a considerable time it was believed the cell was the elementary and basal form of life-the structural condition of formed substance which was indispensable to the reception of vitality, and the wasting enclosed germ, under the specific denomination of nucleus, was held to be, not the residue and remainder of the earlier and more actively vital state, but the seed-germ' which was to lead up to matured vitality. It is now, however, understood that it is exactly those aggregations of bioplasm which have the least trace of an external investment of formed substance that are endowed with the most energetically vital, and especially reproductive, power; and that it is those which have most effectually shut themselves up in an outer case of their own formation that are, on the other hand, the least energetically vital.

The colourless blood-corpuscle of the living animal is essentially the representative and typical form of primary bioplastic aggregation which is employed in the economy of animal organisation, both for reproduction and multiplication of like aggregations, and for the construction of the various fabrics that are finally made for the building up of the body. A very casual reconsideration of the especial character of this little typical workman in the labours of organisation will serve to suggest how marvellously it is fitted for the office it has to fulfil. In the first place, there is its convenient habit of incessant rolling of itself in every possible direction and into every possible shape, and of instinctively insinuating itself wherever it is possible for material substance to find entrance and lodgment; and then, in the next place, there is its no less remarkable habit of incessantly absorbing spherules of organic substance into the restless vortices of its own mass, and of there changing them into formed substance,' the material base of organised textures. Comparatively few colourless corpuscles are seen, at any one