CHAPTER VI.

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

(CONTINUED).

"No more causes of things ought to be admitted, but such as are both true and sufficient to explain the phenomena." SIR ISAAC NEWTON.

EVOLUTION OF GASEOUS MATTERS FROM BLOOD.

[IN our preceding inquiries, physical and chemical, we have been led irresistibly to the conclusion, that motion is not sufficient to account for fluidity, nor rest for coagulation; we have seen that exposure to the air is not alone sufficient to account for coagulation, though it is a favouring circumstance; and that mere confinement from air will not of itself sustain fluidity. We have seen that contact with living tissues is not alone competent to account for fluidity; for, while coagulation occurs in the presence of a living tissue, we have also seen fluidity sustained under certain conditions in contact with inorganic materials. We have seen that temperature is not sufficient of itself to account either for fluidity on the one hand, or coagulation on the other; inasmuch as the normal temperature of the body favours the coagulation of drawn blood, and is yet combined in the body with the circulating fluid blood. We

have seen, in regard to the effects of chemical agents, that while fibrin is evidently held fluid by some chemical principle, it is most clear that this cannot be one of the fixed substances; or it would continue to sustain the fluidity of blood, whether within or without the body.

We are thus driven, by the purest steps of exclusive reasoning, to the investigation of a new point;—namely, Is the coagulation of blood dependent on the evolution of some volatile substance, under circumstances favourable to its extrication ?]

The idea that the evolution of a gaseous product from the blood is the cause of coagulation, was indeed put forward, as has already been stated, by Sir Charles Scudamore and Polli, who supposed, also, that it was to the escape of carbonic acid gas that the process of coagulation is mainly due. Scudamore did not, however, prove this position, but the contrary; for he found that carbonic acid, passed through blood, had no marked effect in retarding coagulation. This important fact, however, both of them did prove: that coagulation proceeds in proportion as carbonic acid and other gases are given off-the most important observation that had been made on the subject since Hewson's remark regarding the effects of exposure to the atmosphere.

On looking back to all that had been done, and to my own investigations, the conviction became more and more powerful that, in principle, Scudamore and Polli were right respecting the escape of some volatile substance, however wrong they might be in detail. In this direction, indeed, all evidence points, as a reference to chapter IV will prove.

[In this chapter, as the details of physical experiments advanced step by step, this view of the evolution

of gaseous matter advanced also so steadily and convincingly, as to become, by mere accumulation of circumstantial evidence, as near to demonstration as such evidence could bring it. Let us follow this chapter step by step, and examine to what it leads.

Temperature, above the standard of the body, quickens coagulation; cold retards it, and, carried to an extreme, altogether prevents it. Water at ordinary temperature added to blood, in proportion above the amount of blood used, retards coagulation, as though by retaining the volatile principle in solution for a longer time. Fluids of greater densities added to blood have the same effect. The vacuum quickens coagulation; the more intensely as the vacuum is more perfect. The same quantity of blood exposed to air over a wide surface, whether in thin stream or in extensive layer, coagulates more quickly than if retained in mass in a small space. Blood occluded from air in the vessel of an animal, or in organic tubes under cold and pressure, is prevented from coagulating. Blood in motion in a closed circuit, or in a vessel, has its coagulation retarded, while by agitation in the open air its coagulation is quickened.

These facts lend irresistible evidence to the truth of the theory now before us for consideration.]

But, even with these strong arguments in its favour, the theory is far from being proved. Every effect which has been noticed might, after all, be only a coincidence. To test the truth of the theory, therefore, became a plain and necessary duty.

In commencing an inquiry in this direction, I felt that it would be most rational and business-like, not at once to examine the nature of the substances thrown off in vapour by coagulating blood, but to ascertain

primarily whether that vapour itself had any influence. The result is given in the succeeding narrative.

Transmission of Blood- Vapour through Blood. I fitted up a simple apparatus as follows. A Wolf's bottle (A) capable of holding three pounds of fluid blood, was fitted with three good corks, so as to make it quite airtight. A bent tube (c) was fitted into one of the corks, so as to descend nearly to the bottom of the bottle by one end, and to be inserted by the other in a smaller bottle (D) placed near the Wolf's bottle. From the other side-opening passed also a glass tube, which

merely dipped into the neck of the Wolf's bottle, and bent over so as to pass to the bottom of another small bottle (F), of the same size and shape as that already mentioned. The two small bottles were also securely corked; but, in addition to the tubes already named as passing to them from the Wolf's bottle, two other tubes (H and 1) emerged from them. When the apparatus was fitted up, it was easy, by means of a small pair of

bellows (G) attached to the long tube (H) proceeding from one of the small bottles, to throw a current of air through the whole of the bottles. The current, commencing in the attached tube (H), passed to the bottom of the small bottle (D), ascended through one of the bent tubes (c) into the Wolf's bottle, descended to its bottom through the long arm of the tube, then ascended out of the Wolf's bottle, passed to the bottom of the other smaller bottle (F), and finally, ascending to the upper part of the smaller bottle, escaped through the open tube (1) into the air.

EXPERIMENT CCXC. Transmission of Blood-Vapour through Blood. When the apparatus was quite in order, I obtained at one gush two pounds of blood from the throat of an ox. An ounce of this blood was poured into each of the smaller bottles, and the remainder into the Wolf's bottle by its middle opening, which was immediately securely closed. The level at which the blood. stood in each bottle is represented in the figure by B. The whole apparatus was now accurately adjusted; and, the blood being still fluid, a gentle current of air was blown through. This current passed first through the blood into the small bottle (D); then through the blood in the Wolf's bottle; and finally, carrying with it the blood-vapour, into the blood in the third bottle (F). The result was in the highest degree striking. The blood through which air was first passed coagulated in two minutes; that in the Wolf's bottle coagulated in three minutes; while the blood in the third bottle, which for a time received the full charge of the vapour, retained its red colour and its full fluidity for eight minutes and a half; as long, in fact, as any vapour could be sent through it. When the vapour failed, and air