CHAPTER V.

EXPERIMENTAL INQUIRY INTO THE CHEMICAL AGENCIES INFLUENCING THE COAGULATION OF THE BLOOD.

"Biassed neither by preconceived opinions, nor attached to particular views, I have desired to look at all things through the laws of induction, and have endeavoured to avoid what is illusory, and to fix my vision on what is real, substantial, and abiding." PROF. EASTON.

A REFERENCE to the first chapter of this essay will recall to the mind of the reader how large a number of experimental inquiries have been made, to discover whether the coagulation of the blood is due to chemical causes.

Of these experiments, but few offer any direct or satisfactory solution of the question; while many have not the slightest bearing upon it. In conducting experiments, there has been too much proneness to consider the blood as if it were a fluid either disconnected from the body, or charged in the body with a variety of chemical substances, which chemical science has in no way shewn to be connected with it. Two classes of inquiries have thus been instituted; one, whether drawn blood can be retained in a fluid state by chemical agents; the other, whether coagulation can be expedited by chemical agents. In this way, blood has been subjected to the action of the mineral acids, of nitrate of potash. nitrate of soda, nitrate of ammonia, nitrate of lime,

nitrate of baryta, bichloride of mercury, chloride of strontium, and a host of other substances which it is not necessary to repeat. In the application of these chemicals, they have sometimes been injected into the circulatory system by the veins, and at other times added to drawn blood. But the results obtained have necessarily been unsatisfactory, and have failed to solve the question of coagulation. It may be true that a strong solution of nitrate of soda prevents coagulation. But to what does this lead? Nitrate of soda should first be proved to exist in the living blood. If it does not exist there, how can it keep the blood in a fluid state? Conversely, does the fact that coagulation follows the injection of bichloride of mercury into the veins, aid us in determining the cause of this phenomenon, as it occurs spontaneously? The question requires no answer.

In the forthcoming researches, I have studied to avoid the empirical line of inquiry, under the conviction that a few decisive experiments, conducted on a systematic and natural basis, would be most effectual in throwing light on the chemical theory of coagulation. In laying out my plans, therefore, I assumed, as a rational basis, the institution of such experiments mainly as might be suggested by a consideration of the component parts of the blood itself, or of the body.

The inquiry, thus arranged, admits of division into two questions.

1. Does the blood naturally contain any agents which have the power of holding the fibrin in a state of solution?

2. If there is an agent in blood possessing this power, why does it lose its influence when blood is drawn and

subjected to those physical influences which we have already proved from experiment to promote coagulation? Let us primarily consider the first of these questions. As the blood floats along in its natural circuit, it has been chemically as well as physically considered as made up of, 1. Organic substances, as fibrin, albumen, red and colourless corpuscles, and oil; 2. Water; 3. Certain free gases, viz. nitrogen, oxygen, and carbonic acid; 4. Soluble salts, viz. lactate of soda, chloride of sodium, chloride of ammonium, carbonate of soda, phosphate of soda, chloride of potassium, and sulphate of potassa; 5. Insoluble salts, viz. phosphate of lime, phosphate of magnesia, phosphate of iron, and the carbonates of lime and magnesia; 6. An exceedingly minute portion of a free alkali, supposed to be potassa or soda.

Regarding these constituent parts, it is to be observed that they cannot all be supposed to exist in the blood at the same time. Thus it would seem impossible for chloride of ammonium to exist in the presence of free potassa or soda; and similar chemical objections might perhaps be urged against the presence of other of the agents named; but, inasmuch as all these have been found in the analysis of the blood, it is to be inferred that their elementary parts at least there existed; and, as we cannot be expected to know intimately what the exact chemical combinations of circulating blood are, those detailed above come fairly under the range of experimental research. If it be surmised that one or other of the individual constituents named above has the power of preventing coagulation, the questions would be, What is this agent? What is the power it exerts? Does it simply hold the fibrin in solution? Or does it give rise to some form of indirect or catalytic chemical action?

In taking up this inquiry, we may first reject such of the blood-constituents as cannot from their nature be supposed to effect any chemical change leading to the constant solution of fibrin. With this view, we may safely set aside the insoluble saline substances; viz. the phosphates of lime, magnesia, and iron, and the carbonates of lime and magnesia, and may base our inquiries mainly on the effects of the soluble salts, the alkalies, the acids, and the gases.

1. SOLUBILITY OF FIBRIN.

In conducting the following experiments, certain precautions were taken bearing on the points mentioned above. First, the fibrin was always obtained from the mixed blood (venous and arterial) of a bullock. Secondly, it was rendered as pure as possible, by being submitted for forty-eight hours to a brisk current of water. Thirdly, in all cases the fibrin, after being dried, was separated into portions of two and a half grains each, which were then minutely divided so as to expose a wide surface, and submitted to the action of a thousand grains of such solution as was employed. Thus, as regarded quantity, the fibrin approached the same proportion to the solution as it does to the blood flowing through the body under ordinary circumstances. Fourthly, the strengths of the solutions were varied; the natural proportion in the blood of each constituent used being, however, always considered as a standard. Fifthly, the chemicals were all carefully tested, and their purity satisfactorily proved. Sixthly, each experiment was repeated several times before any conclusion was drawn from its results.

a. Fixed Alkalies.

EXPERIMENT CLXXI. Fibrin in a

Solution of Potassa. A solution of potassa was made, containing four grains to 1000 of water. In this solution were placed two and a half grains of fibrin. The fibrin commenced to dissolve immediately, and at the end of four hours formed a gelatinous mass, which hung together and floated in the solution, and was coloured slightly brown. In five days it was entirely dissolved.

EXPERIMENT CLXXII. Fibrin in a Solution of Potassa. A solution of potassa was made, containing two grains to 1000 of water. Two and a half grains of fibrin were now added. The solution of the fibrin speedily commenced, and was completed in eight days.

EXPERIMENT CLXXIII. Fibrin in a Solution of Potassa. A solution of potassa containing one grain in 1000 of water, received two and a half grains of fibrin. The effects were almost identical with those in the last experiment; but it required eleven days to effect complete solution.

EXPERIMENT CLXXIV. Fibrin in a Solution of Potassa. A solution of potassa, containing half a grain to 1000 of water, was made to receive two and a half grains of fibrin. In four hours the fibrin had assumed a gelatinous translucent appearance. It required eighteen days to effect complete solution.

EXPERIMENT CLXXV. Fibrin in a Solution of Soda. A solution of soda, containing two grains in 1000 grains of water, received two and a half grains of fibrin. The fibrin was dissolved in seven days.

EXPERIMENT CLXXVI. Fibrin in a Solution of Soda. A solution of soda, containing one grain in 1000 grains of water received two and a half grains of fibrin. Thirteen days were required for complete solution of the fibrin.