III. Intrin- other so closely, that they may be considered as modifications of one and the same substance. sic proper ties of the blood. and car bonate of lime, how Each of these three substances yields, when decomposed, but does not contain, earthy phosphates and carbonate of lime; for the entire blood holds in solution no earthy phosphate, far existent except, perhaps, in too small a quantity to be detected. From these earths it is clear that the bones derive their earthy supply; which, however, it is also clear they can with earthy only do, as in the case of the formation of gelatine, in consequence of a decomposition of the blood as it arrives at the secernents of the bones. in the blood. How the bones are supplied materials. Colouring matter, how separatable. Whence phur, &c. obtain an existence in the blood. Vauquelin endeavoured to separate the colouring matter from the blood by means of sulphuric acid: but this material is not wanted, and does not very well answer the purpose. A method proposed by M. Berzelius in another communication is much simpler as well as more effective*. It consists in placing the clot or coagulum of blood upon blotting paper, to get rid of the serum as completely as possible. The clot is then to be put into water, in which the colouring matter dissolves, while the fibrin remains unaffected; when the water being evaporated, the colouring matter is obtained in a separate state. On reducing this matter to ashes, about of iron can always be separated. It is difficult to determine by what means the iron or the iron, sul- the sulphur, or the elementary principles of calcareous earth, obtain an existence, or the means of existence, in the blood. If these materials were equally diffused throughout the surface of the earth, we might easily conceive that they are introduced through the , medium of food. But as this is not the case; as some regions, like New South Wales, at least on this side the Blue Mountains, contain no lime-stone whatever, and others no iron or sulphur, while all these are capable of being obtained apparently as freely from the blood of the inhabitants of such regions, as from that of those who live in quarters where such materials enter largely into * Ann. de Chim, et de Phys. v. 42. III. Intrinsic proper ties of the the natural products of the soil; it is perhaps most reasonable to conclude that they are generated in the laboratory of the animal system itself, by the all-controlling blood. influence of the living principle. amount of adult. What may be the aggregate quantity of any of these Aggregate minerals in the mass of blood belonging to an adult, has iron in the not been determined with accuracy. The amount of blood of an the iron has been calculated by Parmentier and Deyeux, upon grounds furnished them by Menghini, at seventy scruples, or very nearly three ounces, estimating the average of blood in the vessels of an adult at twenty-four pounds, which is most probably something short of the mark. in any other part than iron exists the colouring matter. Whether iron exists in any other part of the animal Whether frame than the colouring matter of the blood, is in some degree doubtful. Vauquelin seems to have traced it in egg-shells and oyster-shells; and Mr. Brande thinks he has done the same in the chyle and in the serum, and this as largely as in the colouring matter of the blood, which, after all, he thinks contains only a very minute quantity*. But these experiments are too indefinite, and by no means coincide with those of Berzelius, since confirmed by other chemists. If the experiments of Menghini may be relied upon, human blood contains a larger proportion of iron than that of quadrupeds; quadrupeds have more than fishes; and fishes more than birds. But though there can be no longer any question of the existence of iron as a constituent principle in the blood, we are in total ignorance of the part it is intended to perform. It is, perhaps, the colouring material, though, as I have already observed in the physiological proem to the preceding class, even here we are still very much in the dark, and are overwhelmed with contending hypotheses. It is probable that the red particles of the blood contribute to the strength of animals to whom they are natural, as conjectured by Mr. J. Hunter, and that the strength of such animals is in proportion, or nearly What part intended to perform. the iron is III. Intrinsic proper ties of the blood. Form and diameter of the red the blood. so, to their number. Yet such particles are never found in the blood of several classes of animals, as insects and worms: and in those in which they are found, they have often no existence in the commencement of life; for they are not discoverable in the egg of the chick, when the heart first begins to pulsate; nor are they, in any animals, pushed into the extreme arteries, where we must suppose the serum reaches. And hence, whatever their value, they cannot be regarded as the most important part of the blood, or as chiefly contributing to the growth and repair of the system*. Various attempts have at different times been made, to determine the form and measure the diameter of the particles of corpuscles of the blood, but even this does not seem to have been accompanied with very great success. Della Torre, by applying his microscope, detected them, as he thought, to be flat circles or rings with a perforation Hewson's in the centre; and Mr. Hewson ascribed to them the hypothesis: same shape, but represented them as hollow or vesicular, with a dot of red colouring matter in the centre instead of a perforation; so that, if his description could have been substantiated, they might literally have been regarded as the wheels of life moving on iron axles. Mr. Hewson's hypothesis, however, extended much farther; for, by a variety of plausible experiments, he persuaded himself, and many others also, that it is the office of the thymus and lymphatic glands to secrete and elaborate these vesicles which are then carried by the lymphatics and thoracic duct to the arteries, and from the arteries to the spleen which furnishes them with their coloured long since axles. Some of these physiological and microscopic dioverthrown. vertisements however, have been long overturned; while the general shape of the corpuscles has been gravely shown by other exquisite analyses to be globular; the diameter of which, as measured by the microscopical experiments of M. Bauer, is gooo part of an inch; a microscopic dimension, however, which has since been reduced by Bauer's experi ments. 1 * On Blood, pp. 46. 48. ties of the ments of Captain Kater to a part of an inch. M. Bauer has III. Intrin also ascertained, as he thinks, that it is not the centre of sic properthe globule that is dotted, but its outline that is sur- blood. rounded with colouring matter; so that, instead of being annular wheels with iron axles, they are spherular wheels with iron tiers. It is somewhat singular that, in the revolution of science, M. Bauer's views are now sinking below the horizon, while those of Mr. Hewson are again ascending into notice: for the later experiments of M. Prevost, have restored to the red corpuscles of the blood their flat circles and points: and divested them of a globular form. MM. Prevost and Dumas, believe the co- Experilouring matter to be a membrane by which these cor- Dumas and puscles are surrounded. They pursued a dextrous Prevost. method of drying the red particles as soon as separated, and found that when divested of this red matter and rendered colourless, they are of the same size in every animal they examined; being 1.7600 part of an inch. But that, with the colouring matter, the size differs in different animals; being 1.3100 of an inch in man, the dog, rabbit, pig, guinea-pig and hedge-hog; in the ass 1.4200; the cat and man, 1.4800: the sheep, horse, mule, and cow 1.500; and the goat 1.700. These particles have a peculiar tendency to form themselves into lines, as observed by Sir E. Home; the lines resembling in every respect the muscular fibre. Fibrin they found also to be a collection of colourless same kind as the above; the same corpuscles of the corpuscles may be Those of a chick also traced in the white of the egg. We have also still much to learn, not merely in re- Real differ Phil. Trans. 1818, pp. 173. 187. ence between the † Annales de Chimie, in Loco. blood of sic proper ties of the blood. different species undetected. III. Intrin- spect to the real difference between human blood and that of quadrupeds, but the real difference between that of any one species of animal and any other. M. Berzelius observes that "the great agreement in the composition of human and ox blood is remarkable, and explains to us the possibility of the phænomena observed in the experiments in transfusion." But we have a clear proof that the blood of one species of animals differs so much from that of another, either in its principles or their modification, that no benefit can result from transfusion, unless from like kinds to like kinds. Thus, according to several interesting experiments of Dr. Blundell, a dog, asphyxiated by hemorrhage, may easily be recovered by a transfusion of blood from another dog, but is little or not at all relieved if the blood be taken from man*; and the experiments of MM. Prevost and Dumas precisely coincide with this doctrine. Blood, in many re spects, the most im portant animal frame: acted upon by external bodies, volatile and concrete. Upon the whole, however, we cannot but regard the blood as in many respects the most important fluid of the animal machine: from it all the solids are derived fluid of the and nourished, and all the other fluids are secreted; and it is hence the basis or common pabulum of every part. And as it is the source of general health so it is also of general disease. In inflammation it takes a considerable share, and evinces a peculiar appearance. The miasms of fevers and exanthems, are harmless to every other part of the system, and only become mischievous when they reach the blood: and emetic tartar, when introduced into the jugular vein, will vomit in one or two minutes, although it might require, perhaps, half an hour if thrown into the stomach, and in fact does not vomit till it has reached the circulation. And the same is true of opium, jalap, and most of the poisons, animal, mineral, and vegetable. If imperfectly elaborated, or with a disproportion of some of its constituent principles to the rest, the whole system partakes of the evil, and a dysthesis or morbid habit is the certain consequence; whence When imperfect, the great source of morbid habits. * Trans. Medico-Chir. Soc. Vol. 1x. p. 86. |