lopment before it is fully formed. In its first and simplest form, the future red disc exists as a perfectly colourless corpuscle termed "granule bloodcell," consisting of a vesicle with granular contents, which latter may be either of a coarse or fine character; these "granule-cells" have a diameter in the embryo ox varying from about 1 to 13 of an inch; and in the adult human body, when distended with water, their diameter is about 2 of an inch. The contained granules are extremely minute, varying in diameter according to the degree of development from 3ss to the of an inch, and presenting, as in other similar instances, active molecular motion: a nucleus may be detected by treating the granule-cell with acetic acid. In the second and more advanced stage, distinct nucleated cells appear, which are at first colourless, but subsequently attain the yellow tint proper to the fully-formed corpuscles. Thus, the author recognises two "phases" or grades of development in oviparous vertebrated animals, namely, fishes, reptiles, and birds, each phase having two stages; the process of formation may be thus expressed: First phase, granule-cell Second phase, nucleated-cell 1st stage, coarsely granular. The fully-formed blood of the mammifera and man, contains, like the preceding classes, granule-cells, both coarsely and finely granulated, and nucleated blood-cells in the uncoloured stage also exist; it is to these three forms of cells that the somewhat vague name of "lymph" or "colourless" corpuscle has been applied. In mammiferous animals, especially in the horse and elephant, nucleated blood-cells in the coloured stage, have been found; but such corpuscles have not been seen in the fully-formed blood of man unacted on by re-agents. One of the most novel views contained in these memoirs relates, however, to the existence in mammalia and man of a third and higher phase of development, not possessed by the oviparous vertebrata that of the "cellaform nucleus," constituting the red corpuscle of other anatomists, the nature of which will be understood by the following explanation. The author conceives that physiologists, misled by the similarity of colour, have taken for granted, that the red corpuscle of mammalia is the exact analogue of the red corpuscle of the oviparous vertebrata; whilst, as he contends, it really represents only the cellaform nucleus of that body. "The view of the nature of the red corpuscle' of the fully-formed blood of Man and the Mammifera to which I refer is this: the red corpuscle' of the fully-formed blood of Man and the Mammifera is the cellæ form nucleus of the nucleated cell set free by the bursting of this cell itself, and become filled and red by the secretion of globuline and colouring matter into its interior."-Phil. Trans. p. 75. This explanation of the nature of the red corpuscles in mammals is thought by Mr. W. Jones to clear up the long-disputed question as to the existence or non-existence of a nucleus in that class of animals. He says: "Physiologists have accordingly supposed that it (namely, the red corpuscle of mammalia) should contain a nucleus; but though unsuccessful in the attempt to demonstrate one, they have not altogether ceased to believe in the existence of 1847] Blood in the Embryo. 15 an exact analogy between it and the 'red corpuscle' or coloured nucleated bloodcell of the oviparous vertebrata; they have rather had recourse to conjecture to account for the absence of a nucleus.”—L. c., p. 74. In order to form an opinion of the value of this theory, it is necessary carefully to consider the constitution of the blood in the embryo of mammiferous animals and man. It is well known to physiologists that the blood, which at first circulates in the embryo, is colourless, and, which is a most interesting fact, that the blood-corpuscle has at that epoch a nucleus; moreover, there is an abundance of free globules, which are said by some writers to resemble the nuclei of the nucleated corpuscles just noticed. Among these peculiarities of the embryonic blood, the most important is the existence of a nucleated cell; and the questions immediately suggest themselves, as such cells certainly do not exist in the fully-formed blood of the adult, what is their signification, and what becomes of them? These queries have been answered in one sense by that excellent observer, Mr. Gulliver, who considers, as regards the first point, that the nucleated blood-cell of the mammiferous embryo, is the exact analogue of the red corpuscle or coloured nucleated blood-cell of the oviparous vertebrata ; whilst, with respect to the second question, he affirms that "in mammals the nucleus of the red blood-corpuscle soon disappears," and in this way the above-noticed nucleated cell is transformed into the non-nucleated red corpuscle of the adult mammals. From what has already been stated, it appears that Mr. W. Jones offers a very different explanation of this admittedly difficult point of minute anatomy; this writer contending that the nucleated cells burst, the nuclei alone remaining and becoming the red corpuscles of mammalia. In reference to Mr. Gulliver's view of the subject, Mr. Jones observes, with much justice, that "this apology for the absence of a nucleus in the 'red corpuscle' of the fully-formed blood of Man and the Mammifera, would have had weight if the red corpuscle' had been an object persistent throughout life, like a limb or an eye, but as it is an object constantly disappearing and being regenerated, we should expect, if it were really a nucleated cell originally, to meet with it in a stage when it does contain a nucleus."-L. c., p. 74. We cannot quote the reasons adduced by the author in support of his opinions; but it is due to this patient and successful investigator to observe that the facts brought forward have much force, and must form an important element in this question till it is finally settled. Whether his peculiar views of the constitution of the red particles in the fully-formed blood of mammalia be established or not, must very much depend upon the nature of that essential part of the nucleated cell, the nucleus. That this possesses essentially a limiting wall or vesicle, is generally agreed; and thus we have one of the most indispensable conditions, the existence, namely, of an organic membrane, for the production of those endosmotic phenomena attributed by Mr. W. Jones to the so-called cellæform nucleus. In the present aspect of this question, with every inclination to receive with candour the researches of this eminent physiologist, and fully admitting the force of his observations upon the correspondence in size, between the nucleus of the nucleated blood-disc and the red corpuscles of the several mammalia whose blood was examined, we conceive that further researches are required to arrive at a satisfactory conclusion. We regret that our limits will only allow us to make one or two additional extracts from these important "memoirs." The examination of the invertebrate animals has established the important fact, that, contrary to the opinion of those physiologists who conceive that in these classes the nutritive fluid corresponds to the chyle or lymph of the vertebrata, the blood contains true blood-corpuscles, though not in the same degree of development as in the vertebrate division of the animal kingdom. In the crab and in the invertebrata downwards, so far as the investigation has been carried, granule-cells in both the coarsely and finely granular stages, and also nucleated cells in the uncoloured stage, exist; even a slight appearance of colour is detected in the nucleated cells of the crab and lobster. An interesting fact was ascertained by Professor Graham on analysing some of the corpuscles of the crab; namely, that, although colourless," they contained a sensible quantity of iron, perhaps as much as red corpuscles;" thus corroborating the conviction now prevalent among physiologists, that the red colour does not depend on the presence of iron, and also supporting the theory of Liebig respecting the part played by the iron of the blood-corpuscles in the development of animal heat. The general conclusions of the author respecting the blood of the invertebrata, when compared with the circulating fluid of the oviparous vertebrata, and the mammifera, are thus expressed: "In the oviparous Vertebrata, from the Skate upwards, it has been seen that the blood-corpuscle in its different phases of development is essentially similar to that of the Skate. In the Invertebrata, from the Crab down as far as we have gone, it has also been seen that the blood-corpuscle in its different phases of development is essentially similar to that of the Crab. The only difference, therefore, in essential respects, between the blood-corpuscle of the oviparous Vertebrata generally and that of the Invertebrata, is the same as that between the bloodcorpuscle of the Skate and Crab, viz. that in the phase of nucleated cell, the latter does not attain to a decidedly coloured stage. In the phase of granulecell, the blood-corpuscle of the mammifera and that of Invertebrata resemble each other in essential points of structure. In the phase of nucleated cell they also agree in the absence of a decided coloured stage in this respect differing from the blood-corpuscle of the oviparous Vertebrata generally, and of the early mammiferous embryo. But here the resemblance between the blood-corpuscle of the mammifera and that of the Invertebrata ceases. In common with the blood-corpuscle of the oviparous Vertebrata, that of the Invertebrata differs from the blood-corpuscle of the mammifera in not attaining to a decided third phase.”— L. c., p. 104. The account given by Mr. Jones of the corpuscles existing in the lymphatic vessels of man and the mammifera, is of peculiar interest, when taken in connexion with Hewson's description of the genesis of the red corpuscles; it may be proper to premise that the fluid for examinotion was taken from the thoracic duct. "The corpuscles were,-1st, Granule-cells in both coarsely and finely grannlar stages, altogether similar to those of the blood. 2nd. Besides many cells in transition from granule to nucleated phase, nucleated cells in both uncoloured and coloured stages, quite the same as those of the blood. The nucleated cells were fully distended independent of the addition of water, and were comparatively the most numerous of the corpuscles in the lymph; those in the coloured stage being more so than those in the uncoloured stage. Slight as the colouration of 1847] Development of Red Corpuscles. 17 the coloured stage of the nucleated cell was generally, some few cells presented it perhaps in a more marked manner than is usually presented by the same cells as they occur in the fully-formed blood; in this respect approaching to the red nucleated cell of the blood of the early mammiferous embryo. Some even were of an oval shape. 3rd. A considerable number of free cellæform nuclei, both uncoloured and in different degrees of progressive coloration. These free cellæform nuclei were not much affected by the action of acetic acid or water. Lastly, there were seen here and there among the other corpuscles the empty shell of a nucleated cell in the coloured stage, with a free cellæform nucleus beside it as if just extruded by the bursting of the cell-wall. This is a circumstance which may be viewed as additional evidence, and this of a direct kind, in support of the view above given of the nature and origin of the 'red corpuscle' of Man and the Mammifera.— L. c., p. 82. The author concludes, from his researches, that " the corpuscle of the lymph of vertebrate animals is identical with the corpuscle of their blood; in the oviparous vertebrata, it occurs, like the corpuscle of their blood, in the two phases of granule and nucleated cell; whilst, in man and the mammifera, it occurs, like the corpuscle of their blood, in the three phases of granule-cell, nucleated cell, and free cellæform nucleus." It is further remarked, and the observation is one of much physiological interest, that the fluid of the thoracic duct of a mammiferous animal may, in consequence of the relatively great number of nucleated cells and of the small number of free cellæform nuclei it contains, be compared with the blood of the same animal in its embryo state.-(L. c.) It will not escape the reader how closely these observations bear upon the theory of Hewson. There are doubtless some discrepancies between that theory and the account of Mr. W. Jones, which that gentleman has pointed out; one disagreement being that, whereas Hewson concluded the corpuscles he detected in the juice of the lymphatic glands were merely central particles,' the author we are quoting has ascertained that they are in reality nucleated cells, having very distinct nuclei, and extremely pale cell-walls: "in consequence of this, Hewson appears to have overlooked the cell-wall and distinguished the nucleus alone, but when the cell-wall had already become evident around the nucleus by having acquired colour, he naturally supposed that it was a new formation." (L. c., p. 83.) But, notwithstanding this and some other discrepancies, we regard these researches as confirmatory of that which is the fundamental part of Hewson's great theory, namely, that the red corpuscles of the blood are formed or manufactured in the lymphatic sysIf this become an established principle in physiology, as we ourselves believe it will be, provided the lacteal apparatus be included in the term lymphatic system, then may the patient, reiterated investigations of our distinguished countryman, Hewson, and the great truth they will have mainly contributed to elicit, be regarded as one of the most splendid additions the science of organisation has ever received. tem. Before dismissing the consideration of the red corpuscles, we must solicit the attention of our readers to Hewson's experiments on the curious changes these bodies undergo when placed in water and saline solutions. In the following experiment the influence of water in distending the corpuscles, and in making them spherical, whatever may have been their previous form, is described. No. 107 2 "Take a drop of the blood of an animal that has large particles, as a frog, a fish, or what is still better, of a toad; put this blood on a thin piece of glass, as used in the former experiment, and add to it some water, first one drop, then a second, and a third, and so on, gradually increasing the quantity; and in proportion as water is added, the figure of the particle will be changed from a flat to a spherical shape. When much water is added, the vesicle will by degrees become thinner and more transparent, and will at last be dissolved."—Hewson, p. 222. The latter part of this account contains an error, for the red corpuscles are not actually dissolved by water; they are thereby only deprived of their colouring matter, a fact first observed by Dr. Young. The effects produced by saline solutions are thus accurately noticed: "If a saturated solution of any of the common neutral salts be mixed with fresh blood, and the globules (as they have been called, but which, for the future, I shall call flat vesicles) be then examined in a microscope, the salt will be found to have contracted or shrivelled the vesicles, so that they appear quite solid, the vesicular substance being closely applied all round the central piece. In proportion as the solution of salt is diluted with water, it has less effect, and when diluted with six, eight, ten or twelve times its quantity of water, it produces no change in the figure of the vesicles, whose flat shape can then be seen, even more distinctly than when mixed with the serum itself."-L. c., p. 229. A little consideration is sufficient to show that these experiments? which by their delicacy rival some of the more minute manipulations of chemistry, contain the germ of the important discovery subsequently made by Dutrochet as to the absorbing powers of organic membrane; and they also afford the best proof that can be adduced to prove the correctness of the doctrine now universally admitted, that the blood-corpuscles are in fact floating cells. It is true that Hewson himself did not draw any such brilliant inferences from his precise and often-repeated researches; what he might have done, if his life had been longer spared, it would be now vain to speculate. But although these great results escaped him, this profound physiologist firmly established a principle in the physiology of the blood, of which the importance is only now imperfectly comprehended: we allude to the fact that the normal figure of the red corpuscles is preserved by the serum, or, to speak more accurately, by the salts held in solution in that fluid. In answer to the questionWhence is it that the serum has the property of preserving the flat form of the blood-discs? Hewson replies, "it is principally by the salts of the serum that this effect is produced, as is proved by adding a small quantity of any neutral salt to water, when the water is no longer capable of dissolving those particles, nor does it alter their shape when the salt is used in a certain proportion."-P. 229. All these remarks show how powerfully the red corpuscles must be affected, and especially in disease, by the qualities of the liquid vehicle in which they are habitually placed; not merely as regards the influence exerted upon their colour by the salts of the serum, but likewise with respect to their form, and those other physical properties, by which their attraction for each other is, doubtless, greatly modified. Our notice of these "Experimental Inquiries" has already extended so far, that we have only space for one or two passing allusions to Hewson's description of the Lymphatic System, which, although containing, mixed |