124

THE MINERAL CONSTITUENTS OF BLOOD.

Comparison of To the mineral substances in the cells and plasma of the

the mineral

constituents of blood respectively, attention should be particularly directed, since they indicate the functions of these portions.

the cells and

plasma.

The amount of inorganic matter in the cells and plasma, respectively, of 1000 parts of blood being nearly the same, the table shows that there is more than twice as much chlorine, and more than three times as much sodium in the plasma as in the cells. It may thence be inferred that the chloride of sodium is, for the most part, in the plasma. Moreover, there is six times as much phosphorus, and more than ten times as much potassium, in the cells as in the plasma; and therefore it may be inferred, since potash is required to so great an extent in the nutrition of the muscular system, and phosphorus as an element of the phosphorized oils in the nervous, that the cells have a direct functional relation to those important mechanisms, and this in addition to their duty of introducing

oxygen.

Functions of the mineral

constituents of the blood.

The mineral constituents of the blood discharge very different duties, some, either directly or indirectly, acting functionally, others as histogenetic bodies. Thus the alkaline properties of the blood are due to the presence of the carbonate and phosphate of soda, and this latter substance enables the serum to hold in solution carbonic acid, and thus it maintains a relation in the respiratory operation. But the phosphate of lime discharges a true histogenetic function, since upon it the bony system depends for its nutrition. The mutual relations of these substances are, of course, very complex, though often of importance. Thus, of the two just mentioned, the phosphate of soda enables the serum to hold the phosphate of lime in solution.

The tawny coloring matter of serum differs from cholepyrrhin in not Coloring mat- yielding the characteristic reaction of that body. The tint ter of serum. sometimes becomes quite deep, owing to several different causes, such as the undue accumulation of the coloring matter of urine, through disturbance of renal action, or from bile pigment, as in icterus.

The gases which can be disengaged from the blood occur in the cells, according to Magnus, a statement which, however, is very far from being

FUNCTIONS OF THE CONSTITUENTS OF BLOOD.

125

substantiated: they are carbonic acid, oxygen, and nitrogen. Gases of the He found that this liquid can absorb once and a half its vol- blood. ume of carbonic acid, and that in arterial blood the acid to oxygen is as 16 to 6, in venous as 16 to 4.

proportion of that That the oxygen

That the

is very loosely retained is shown by the circumstance that it may for the most part be removed by exposure in a vacuum. The other gases may be withdrawn by a stream of hydrogen.

At a temperature of 98°, water absorbs scarcely one per cent. of its volume of oxygen gas, but the blood can take up from 10 to 13 times as much. This is accomplished by the coloring material. The amount is independent of variations in the pressure of the air, which would not be the case if the gas were received into the circulating fluid by mere solution. This is the opinion of Liebig, by whom it is regarded as being to some extent substantiated by the fact that the respiration is accomplished with nearly the same result, so far as the absorption of oxygen is concerned, at considerable heights above and at the level of the sea, and that no more oxygen is received from an atmosphere very rich in that gas than from the ordinary air. However correct this view may be, the facts cited in its support are very far from being undeniable.

The preceding chemical examination of the special constituents of the blood leads us next to consider the general functions of this liquid in the aggregate.

General state

ment of the

functions of

the different constituents of

the blood.

In this general sense, the blood discharges the following offices. Its albumen has the duty of giving origin to all the plastic tissues of the system. From it, for example, by cell action, as explained in treating of lacteal absorption, fibrin arises fibrin, which is used for the renovation and repair of the muscular tissues. The discs have a relation with the function of respiration; they obtain oxygen in the pulmonary circulation, and carry it through the system. They contribute, moreover, to the development of muscular fibre, and also nervous material, and this not alone as regards the coloring matter of those tissues. The fats are necessary in the production of fibrin and for the nuclei of cells; but, besides these histogenetic relations, they eventually, with the exception of liver-fat, undergo oxidation, and so minister to the support of a high temperature. Of the saline substances, common salt promotes digestion by aiding in the preparation of gastric and pancreatic juices; the phosphate of soda enables the plasma to hold carbonic acid in solution, and carry it to the lungs.

It is interesting to observe the limits of variation which the blood may present in disturbed or diseased conditions. In inflammations, the fibrin may increase fourfold; in typhoid fevers it may diminish to less than one half, and from these variations special results may arise. Thus diminution of its fibrin disposes the blood to preternatural oozing or fa

126

CHANGES IN THE CIRCULATION.

cility of escape. So also the cells have been known, in cases of chlorosis, to sink to one fifth of the healthy amount. The albumen, too, exhibits like variations. In Bright's disease it greatly diminishes, much of it escaping in the urine by the straining action of the kidneys.

Changes occur

Thus constituted, the blood, by a mechanism to be described in the next chapter, passes from the heart alternately to all parts ring during the of the system, and alternately to the cells of the lungs, givcirculation. ing rise to what have been termed the greater and less circulation, or the systemic and the pulmonary. In the systemic circulation, the blood, which leaves the heart in an arterialized condition, or associated with atmospheric oxygen, gives up that element to the various tissues as it pervades them, and accomplishes a double result: the removal of all those particles which, having discharged their duty and undergone partial or perfect interstitial death, are ready to pass away, and also the liberation of a great amount of heat by the destructive oxidation; so, at the same time, the wasted matter is removed and advantage taken of it to raise the temperature of the body. This done, the blood makes its way back to the heart, following the channel of the veins as they successively converge into trunks that are larger and larger. At the moment of surrendering its oxygen and receiving the various products of combustion, a change of color occurs. The bright crimson turns to a deep blue, and the blood presents itself of that color at the heart.

It now undergoes the less or pulmonary circulation. Leaving the heart, it passes over the air-cells of the lungs, and is there exposed to the aerating action of the atmosphere. From the interior of the cells the discs receive their supply of oxygen, the plasma surrendering up carbonic acid and the vapor of water. The color now changes back from the blue to the scarlet. In this condition it returns to the heart, to be distributed in the systemic circulation once more.

Less obvious

During this double round an incessant change is taking place in the constitution of the blood: it is undergoing a continuous metbut important amorphosis. In some respects, as, for instance, in color, changes. this is obvious enough. But the invisible changes infinitely exceed in importance and amount those that are obvious to the eye. All the soft tissues, since they are wasting away, require repair. This, inasmuch as it is accomplished either directly or indirectly by the albumen of the blood, gives rise to a constant drain of that substance, and demands a constant supply, which is provided by nutrition or stomach digestion.

The cells, which constitute the other chief portions of the blood, are Translation of necessary to the production of a high temperature, by conoxygen by the stantly transferring oxygen from the cells of the lungs to every part of the body; carriers of oxygen they have been

cells.

GRADUAL DESTRUCTION OF BLOOD-CELLS.

127

truly called. That this is one of their duties has been proved experimentally, for a solution of albumen or the serum has but little power of absorbing oxygen, scarcely exceeding water itself in that respect, but the discs condense it at once. The change of color they exhibit as they alternately gain or lose that element, is in itself a proof of this fact, as is also the action of serum or blood-discs respectively on a measured volume of air contained in a jar. If the discs be in the venous or purple condition, they quickly absorb oxygen from the confined air, whichı therefore at once diminishes in amount, but the serum, or a solution of albumen, produces no such effect. The plasma serves, therefore, for the general nutrition of the system, and the discs, by transferring oxygen from point to point, discharge that part of their duty which is connected with the production of heat.

Transitory du

cells.

But the discs, though of a flattened form, are truly cells, and all that obtains in the case of cell life and cell action obtains for them. They have not a duration at all comparable to the ration of the duration of the system, but are constantly coming into existence and disappearing. Each is an individual having its own particular history, its time of birth, its time of maturity, its time of death. Each passes through a series of incidents proper to itself. Originating as has been described, they grow at the expense of the plasma, and in this regard it serves for their nutrition as well as for that of the body generally.

On exposing blood-cells to oxygen and carbonic acid gases alternately, there is not only a change in their shape, which becomes corrugated and star-like, but also in their chemical constitution, so that, after such an exposure of nine or ten times, they are entirely destroyed. Such alternations occurring in the system doubtless lead to the same result, though more slowly, since the oxygen is presented in a diluted condition.

The corrugated and star-like blood-cells abound in the blood of the portal, though not in that of the hepatic vein. If their aspect arises from their tendency to disintegration, this is no more

Fig. 50.

Stellated blood-cells magnified 500 diameters.

Dying cells.

than might be expected in view of the functions of the liver. That the stellated aspect is an indication of a commencing disorganization, or other profound change, may be illustrated by an examination of the action of water on normal blood-cells, which, if they be exposed to that liquid, undergo a distention; their thickness increasing more rapidly than their diameter, they lose their concavity, become convex, and at last appear as spheres of a less size than the original discs. When

128

ASSOCIATION OF HÆMATIN AND OXYGEN.

the quantity of water they have received has distended them to their utmost capacity, they then are invisible; but when it is withdrawn from them by establishing exosmosis through the addition of saline substances, they may reappear in the corrugated or star shape, as seen in the photograph, Fig. 50.

Action of hæm

by indigo.

With respect to the action of the hæmatin, it may be observed, that other nitrogenized coloring materials present a similar relaatin illustrated tion to oxygen. As an example, indigo may be mentioned. I consider that the properties of this substance illustrate in a significant manner the properties of hæmatin in the system. Indigo occurs in the leaves of the plant which yields it in a yellow and soluble state. It is easily extracted from them by maceration in water. Exposed to the air, it absorbs oxygen, becomes insoluble, and simultaneously gains a deep blue tint. So lightly is the oxygen thus united to it, that by exposure to very feeble agents it surrenders it up, and repasses into the yellow and soluble condition. Once more exposed to the air, it turns blue, and once more may have that color removed from it by taking its oxygen away. For many times in succession its tint may be thus changed, and made yellow or blue at pleasure.

From this we perceive in what a loose manner oxygen is held by such a coloring material; how readily it surrenders it, and how readily it recovers it. Such a union can scarcely be called an oxidation or a combination; it is rather an association.

oxygen and hæmatin.

All this is precisely what occurs in the case of hæmatin. It takes up Fecble union of oxygen with rapidity as it goes over the cells of the lungs, and turns scarlet; it surrenders that oxygen with equal facility as it passes the systemic capillaries, and turns blue. This change of color is incessantly taking place; it is now red, and now blue, as the cells are passing in the greater and the less circulation.

transference

of oxygen by

Formerly it was supposed that, in the act of respiration, oxygen from Reception and the air united with carbon of the blood or of the cells, and carbonic acid formed, a combination or perfect oxidation the blood-cells. taking place in the lung. But, if this were true, the temperature of those organs should be higher than that of the rest of the body, and this is by all admitted not to be the case.

The cells are therefore carriers of oxygen. They receive that vivifying principle as they move over the respiratory cells, and, freighted with it, pass to all parts of the body, not united with it, nor disorganized, nor burnt up by it, but holding it loosely, and ready to give it up and go back again for a fresh supply.

The sac containing the hæmatin offers no kind of resistance to these exchanges. It will be fully demonstrated in the chapter on respiration that this is the case. Thick pieces of India-rubber, stout animal mem