Sidebilder
PDF
ePub

COLOURLESS BLOOD-CORPUSCLES.

91

In the frog, the red corpuscles consist of a delicate membrane forming a cell, within which is a granular nucleus. The nucleus is globular, and much smaller than the cell; and the space between the inner surface of the cell and the outer surface of the nucleus is filled by fluid, holding the colouring matter in solution. The nucleus cannot be detected in the red corpuscles of the human body, but analogy suggests that its structure must be of the same general character as in the animals, in which these corpuscles are of larger size.

A question has arisen, whether what have been termed the colourless corpuscles of the blood be a distinct set of bodies, or merely the

[merged small][merged small][graphic][merged small][merged small][merged small][merged small][ocr errors][merged small]

PHASES OF THE HUMAN BLOOD-COR

PUSCLES-after Wharton Jones. a and b, granule cells in the coarsely and finely granulated state; c and d, nucleated cells; c, without colour, and d, with colour; e, free cellæform nucleus, a perfect red corpuscle.

The colourless corpuscles

red corpuscles in a less developed state. are spherical bodies, destitute of colour; they are cells composed of a very delicate membrane, and the cells are nucleated. The addition of weak acetic acid renders the cell-membrane, the nucleus, and the nucleolus more distinct, by dissolving some granules contained within the cells. The colourless corpuscles slightly exceed the size of the red corpuscles in mammals, but not in the other vertebrata. They are thought to be essentially the same as the nucleated particles found in lymph, and in the chyle. They are fewer in number than the coloured corpuscles, being, it is said, in the proportion of one to fifty. In inflammatory states of the blood they become more abundant; and, after great loss of blood, the proportion of these colourless corpuscles is greatly increased. Without entering upon the difficult question, what is the relation between these colourless corpuscles and the red corpuscles, it will be sufficient to say, in the meantime, that the weight of authority is in favour of these two kinds of corpuscles

.92

COLOURLESS BLOOD-CORPUSCLES.

being identical in species, that is, merely different stages of one organism.

According to this view, then, to quote a passage from Todd and Bowman's Physiology: — "In the earliest periods of foetal life, the blood-corpuscles, as is shown by the researches of Vogt, Kölliker, and Cramer, originate in the same way as the elements of the tissues, from nucleated cells, which are the same, in point of constitution, as the colourless corpuscles; with this exception, that they contain, between the nucleus and cell, a considerable number of granules, which are largest at the earliest periods of embryonic life. At later periods similar nucleated cells are generated in the liver, as first pointed out by Weber, and from these sources supplied to the blood. In this fluid they undergo a transformation into the completely formed blood-corpuscles, by the removal of the granules, the increased development of the nucleus, and the generation of colouring matter, excepting in the mammiferous corpuscles, whose ultimate change seems to consist in the complete absorption of the nucleus, according to Kölliker, or the removal of the wall of the cell, according to Wharton Jones.

"Now, as there can be no doubt that, in the adult, the lymphatic and chyliferous systems afford a source for the constant development of particles identical with the colourless corpuscles, and as such corpuscles are always found in considerable proportion in the blood (being more numerous under circumstances unfavourable to normal changes, as in inflammations), it seems very reasonable to infer that similar transformations of colourless into coloured particles are going on in the adult as in the embryo, and that the lymphatic and lacteal systems must be at least one, and that a fertile source, from which red corpuscles are being continually supplied to the blood." p. 639.

There is no foundation for the idea that each blood-corpuscle gives origin by a species of reproduction to new blood-corpuscles. The blood-corpuscles probably decay by simple solution, though it does not yet clearly appear what substance in the blood, or in the body, results from their decomposition. The various colouring matters throughout the body have their origin, as is probable, from the colouring matter of the blood.

It is not unreasonable to suppose that the red corpuscles are floating gland-cells, as they are, in all essential points of structure, like the secreting cells of true glands. Their secretion is hæmatine; that is to say, not merely the colouring matter, but the entire contents of the blood-corpuscles, of which iron is probably an essential part, since even the blood of the invertebrate animals contains a sensible quantity of iron, and that when no colour is distinguishable.

Liebig's idea as regards the important function performed by the

WASTE AND REPAIR OF THE BODY.

93

red particles, by means of the iron which they contain, must be spoken of when we come to the function of respiration.

Salts of the Blood. - With respect to the saline matters of the blood, the analysis we have given makes the proportion, estimated together with that of extractive matters, no more than about eight parts in the thousand, or somewhat less than one per cent. But, according to other analyses, this part of the blood amounts to more than one and a half per cent. The principal salts of the blood are the albuminate of soda; other alkaline salts, as the carbonate, phosphate, and sulphate of soda, and the chloride of sodium; earthy and metallic salts, as the phosphate of lime, the phosphate of magnesia, the phosphate of iron, the carbonates of lime and magnesia, and the peroxide of iron. In the muscular flesh, which constitutes the chief bulk of the living frame, and that, as before stated, which, from its activity, requires the most frequent repair, there is a considerably less proportion of saline matter than in the blood. Whence it may be inferred that, by the products of digestion, a larger amount of saline matter is thrown into the blood than is required for the nutrition of the chief solids; and therefore, that a great part of the saliue matter given off from the blood by the kidney, is merely the excess of what has been received by the blood during digestion, and that it has never entered into the constitution of the living frame.

Some of the salts of the blood are essential to the secretions, particularly to the bile and to the gastric juice.

Waste and Repair.-The continual waste of the constituents of the blood is supplied by the products into which the food received into the stomach is converted. Together with the products of digestion, the contents of the lymphatic vessels, originating in almost every part of the living frame, are poured from the thoracic duct into the circulating system. Perfect chyle is collected from the small organs existing abundantly in the folds of the mesentery, termed mesenteric glands (see page 62), by vessels which gradually unite into a single trunk, by the union of which with the lymphatic trunks, from the pelvis and the lower extremities, the thoracic duct, as already has been shown, is formed. The same general plan pervades the whole of the vertebrate division of the animal kingdom; that is, there is a lymphatic system of vessels pervading the body at large, and a chyliferous system of vessels originating in the intestines, both of which systems unite in a common trunk, which communicates directly with the sanguiferous system. In birds, reptiles, and fishes, however, there are no mesenteric glands. Although it cannot be doubted that important changes take place on such products of digestion as are taken up by the lacteals within the mesenteric glands, it is plain, from the fact just stated, that these

94

PROPERTIES OF LYMPH.

organs are not essential to the formation of perfect chyle; that is to say, a chyle perfectly capable of imparting the required nutritive properties to the blood. One remarkable difference exists between the chyle in mammals, and that in the three remaining divisions of the vertebrata; namely, that in the former it is an opaque fluid, and throughout the latter quite transparent.

[ocr errors]

Lymph. There is contained in the lymphatics, and also in the lacteals, when digestion is not going on, the transparent and almost colourless fluid termed lymph. In this lymph there are a number of colourless nucleated cells, which seem, as before hinted at, to be identical with the colourless corpuscles of the blood. In the chyle the same corpuscles are found; but, in addition to these, there is what has been termed the molecular base, a finely granular matter, which varies with the amount of fatty matter in the food. To the presence of this molecular base the milky colour of the chyle is said to be due. To the absence or deficiency of this substance is to be ascribed the transparency of the chyle in birds, reptiles, and fishes. If a dog be fed on food from which fat has been carefully excluded, the chyle is not milky, but whey-like or transparent.

The molecular base is present in the chyle collected at the very origin of the lacteals in the intestinal canal. Both lymph and chyle, when taken from the vessels, undergo spontaneous coagulation. This coagulation depends on the presence of liquid fibrine, as in the blood; while the coagulability bears a close relation to that of the blood in the same animal. The serum of the lymph is an albuminous fluid. Saline matters of the same kind as exist in the blood are found in the serum of the lymph; there is also a trace of fatty matter and of iron. The coagulation of the chyle depends also on the presence of fibrine; and the serum of the chyle contains more albumen and more fat than the serum of the lymph.

per cent.

Thus, lymph differs from blood, in having no red corpuscles, and having a less proportion of albumen and fibrine. Chyle differs from blood in the same respects, and also in containing a large proportion of fat, which may amount, it is said, to as much as one and a half Chyle differs from lymph in containing more albumen and much more fat. Of the fitness of the chyle, derived from the process of digestion, to sustain the nutritive properties of the blood, we have to speak hereafter. One point of difficulty arises, to explain what becomes of the large proportion of fatty matter which it contains. Fat is not a poteine compound; it cannot pass into fibrine, albumen, or cascine—it is a non-azotised principle; but though incapable of contributing to the repair of the more important textures, it is quite capable of supporting animal temperature by the process of slow combustion, termed eremacausis. It seems probable, then, that the superfluity of fatty matter, supplied by the chyle to the blood is

CIRCULATION SUBORDINATE TO THE BLOOD.

95

burnt off in the process of respiration, so as essentially to maintain the animal temperature.

What, then, is the use of the lymph which is poured so abundantly into the blood from the thoracic duct? As the lymph contains so many of the constituents of healthy blood, it is impossible to doubt that the addition of the lymph is a source of repair to the blood; but the question remains, What is the source of the lymph? By far the most probable supposition is, that the lymph of the lymphatic system is nothing more than the residue of the liquor sanguinis after the repair of the textures. The lymph is blood, deprived of the whole colouring corpuscles, and of part of its albumen and fibrine. The liquor sanguinis, or blood without the colour ing corpuscles, exudes through the walls of the capillaries, and comes into contact with the ultimate morphological constituents of the tissues, which attract from it what is necessary for their repair; while, by the lymphatics, which are, in fact, a system of veins subsidiary to the red veins, the residue is conveyed to the thoracic duct, to be again mingled with the blood.

From the view now exhibited of the composition of the solids, of the blood, and of the lymph and chyle, we obtain the means of

[merged small][ocr errors][merged small][subsumed][merged small][merged small][graphic][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small]

judging of the important place held by the blood in the animal economy. The circulation

-wonderful as it seems when considered

« ForrigeFortsett »