SECT. II. CHAP. V. weight of blood in the frame, that in bleeding, upwards of one pound, or two pounds' weight of blood, or as we have seen even forty ounces, or three pounds and a third, or still more, should be subtracted with impunity.(i) OF THE 11. Vitali The vitality or life of blood has long been a subject of dispute. Harty of blood. vey insisted upon its being the principal if not the sole cause of life. (g) whilst others have maintained that it has no vitality (r) Modern physiologists admit this vitality, but deny that it is the sole cause of life. (8) It seems certain that the blood when oxygenated in the lungs is the exciting power of the heart, and that without such excitement the heart and the brain would instantly cease to act and death ensue,(t) and that parts die if deprived of a supply of blood; but it has been observed that although this may prove that blood is necessary as a material agent to maintain the life of parts, yet that it is not therefore necessarily proved that it is itself vital.(u) But it is admitted that the essential nature of life is an impenetrable mystery, and some have unphilosophically observed that it would be an inquiry not to be pursued for any useful purpose.(x) Dr. Bostock observes that Mr. Hunter's celebrated hypothesis of the life of the blood is founded upon the principle, that a fluid is capable of organization, and that it may possess functions either identical with or very similar to those which are the most characteristic of the living animal solid. According to this doctrine, the blood is supposed not merely to be the substance which gives life to the animal, by carrying to all parts what is necessary for their support and preservation, but that it is properly itself an organized living body, and even the peculiar seat in which the vitality of the whole system resides.(y) 12. CoaguCoagulation. When any quantity of blood is extracted from the cirlation or culation, and allowed to flow into a vessel, in the course of some minutes crassamen- it separates into two parts, namely, a thin watery fluid, of a whitish sometum.(z) what opaque colour, called the serum, and a solid substance of a deep red colour, assuming more or less the form of the vessel in which it is deposited. This is called the crassamentum or cruor. The crassamentum, again, is composed of two materials, first, the fibrin, or the coagulable lymph, as it is called, which is of a pale colour, and the red globules, by which, before coagulation, the whole blood is coloured, but which, from their greater specific gravity, sink to the bottom of the crassamentum. When the crassamentum is cup-shaped with an inverted margin at the top, has a coat of buff on its surface, and is tenacious when pulled asunder, the blood is considered inflammatory.(a) The coagulation of the blood has been considered by some as quite unconnected with its vitality or life, but as entirely a chemical result, attributable to the escape of carbonic acid.(b) But as regards coagulation it is important to observe, that blood coagulates slowly, in regular proportion to the tonic state, or that condition of the system in which the (i) Ante, 154, 155, note (y;) Dr. Stevens on Blood, 338; Copl. Dict. 178. (q) 2 Good, 42; and see Dr. Pring's Principles of Pathology, &c.; Dr. Turner's Chemistry, 551; Stevens on the Blood, 119, 121; " For the life of the flesh is in the blood," Leviticus, xvii. v. 21; 2 Dungl. Phy. 507. (r) El. Blum. 32, 33, 62, 63; 1 Bell, 503 to 521; but see note of Charles Bell, p. 521. (s) But see 1 Bell, 521, note of Dr. C. Bell, observed upon in Stevens on Blood, 119 to 135; Dr. Elliotson's note to Blu menbach, 61, 62. (t) Ante, 92; 2 Good, 22 to 24. (z) As to the coagulation of the blood, see in general Dr. Scudamore, Dr. Davy, Ed. Med. Journ. vol. xxx. 248; 2 Dungl. Phy. 46. (a) See, farther, El. Blum. 7, 12. (b) El. Blum. 13. But see Dr. Stevens on Blood, 5, 6, who seems to attribute coagulation to the loss of the vitality of the blood; 2 Dungl. Phy. 507. vital powers are strongest. (c) As affording evidence in some cases, whether or not the death has been occasioned by criminal means, the subject of coagulation has been treated as exceedingly important to be examined.(d) The coagulated blood is also considered as a source of useful information to medical practioners; for certain appearances of the blood after its coagulation are a general indication of its inflammatory or non-inflammatory state.(e) When the temperature of the blood, either after death or when separated, has fallen from its medium of about 96 to 98 Fahrenheit, it usually then begins to separate into two portions. The coagulation is first. formed from the surface, whence exudes, as it were, a fluid of a yellowish slightly red colour, denominated serum; the more abundantly this exudes the greater is the contraction of the glutinous coagulum, which has received the appellation of crassamentum.(f) Soon after it leaves the vessels, if it be suffered to remain at rest, blood coagulates when it has escaped from the human body, whether warm or cold, in the air or in vacuo, diluted within certain limits or undiluted, at rest or in motion.(g) Some have supposed that venous blood coagulates more slowly than arterial, and that it contains less fibrin, but that its specific gravity is greater; however, Dr. Bostock observes, that these points are not very accurately ascertained.(h) Large quantities of blood are found fluid in every dead body, and the blood of the vessels is found most frequently in opposite states, fluid in one part, coagulated in another; but it is said that the blood is always coagulated in the heart after death by natural means.(i) The blood generally coagulates in the living human body on escaping from its vessels, and even in its vessels if its motion be prevented by ligatures. It almost always coagulates also in the vessels running through healthy parts to others in a state of mortification, and in large vessels adjoining to pulmonary tubercular abscess, in which case the final cause, namely, prevention of hemorrhage, is evident. The immediate cause, however, in all these examples is unknown. Blood, when removed from a healthy person, coagulates in from three or four to seven minutes.(k) The non-coagulation of the blood after death proceeds from arsenic, opium, and some other narcotics, and from lightning() and electricity, (though Dr. Scudamore found it to coagulate as usual in the latter case,) from hard running, anger, or a blow in the stomach, all three of which deprive the muscles of their usual stiffness, which may depend upon chemical changes. The admixture of opium with the blood has been said to prevent its coagulation; but Dr. Scudamore found that the admixture of prussic acid and belladonna, both strong poisons, had no such effect, but that many salts weaken or prevent its coagulation.(m) Dr. Bostock, in an early part of his work, stated, that strong agitation prevents the coagulation of the fibrin.(n) But in a subsequent volume he candidly admits that Dr. Davy had shown that that position is incorrect, and that notwithstanding strong agitation the blood actually assumes the solid form, but that being in small particles separated only, it is diffused through the fluid, and thus escapes observation.(0) It appears that carbonic acid is disengaged during the coagulation of the blood; that blood which has the highest specific gravity coagulates the most rapidly; CHAP. V. OF THE CHAP. V. OF THE Of the clot cake or tum, and of the fluid or serum. that coagulation is promoted by the blood being drawn slowly from the vessel, and by being received into small shallow cups, probably in consequence of its heat being in this case abstracted more rapidly. When blood exhibits the buffy coat it coagulates more slowly than when it is extravasated or remains in the blood vessels; after they have lost their vitality it coagulates very slowly. Drs. Bostock and Scudamore consider that heat is disengaged during coagulation, although in small quantity only.(p) But Dr. Davy maintains that heat is not extricated during the coagulation either of fibrin or of serum;(q) and Drs. Bostock and Scudamore observe that it has been found that the quantity of fibrin is considerably increased in blood, that it exhibits the buffy coat, and that the proportion of fibrin is then much nearer the surface of the clot than at its lower part.(r) Putridity. It has been said, that blood when drawn from the young is sooner putrid than when drawn from old persons, and that such result probably arises from its inferior qualities,(s) and yet it might have been supposed that the blood of youth having to serve two purposes, namely, growth as well as nutrition, would be endowed with even higher qualities, and that hence, if the result be correct, it must be attributable to some other cause. Upon the coagulation of the blood it separates, as we have just seen, into two parts, namely, first, into a red mass floating in, secondly, a yelcrassamen- lowish fluid. The red part is called the clot or crassamentum, and the fluid part the serum; a portion of the serum always remains attached to the clot. It has been supposed that the crassamentum amounts to about one-third of the weight of the serum, but the proportions vary considerably in different individuals, and even in the same individual at different times,(t) and others say that they are nearly of the same weight. Arterial is said to differ from venous blood in containing a larger proportion of crassamentum, and it is supposed that the crassamentum is immediately produced from the chyle which enters the vessel just before the blood is exposed to the action of the air in the lungs.(v) 13. Of the fibrin or gluten, or coagulable lymph of the crassamentum. The crassamentum, when removed from the serum, appears under the form of a soft solid cake, of such consistence as to bear cutting with a knife. It frequently assumes, and actually has, a fibrous appearance, very similar to the pure muscular fibre, though it is said to differ from it in its minute particles. It has been designated by several names, as coagulable lymph, gluten,(y) fibre of the blood, and fibrin. The latter name is in more general use.(z) This coagulation is generally attributed to rest and exposure to the atmosphere, but sometimes the blood will coagulate internally, and on the other hand agitation or the introduction of certain neutral salts and poisons will prevent it. (a) But the actual cause of coagulation of the fibrin or gluten has never been satisfactorily explained.(b) Sudden death from lightning and electricity, a blow upon the stomach, or injury to the brain, the bite of a venomous animal, such as the viper and the rattlesnake, some acrid vegetable poisons, as laurel water, also excessive exercise, and even violent mental emotion, when they produce the sudden extinction of SECT. II. life, prevent the usual coagulation of the blood from taking place.(c) CHAP. V. There is a singular coincidence in these cases between the want of coagulability in the fibrin of the blood, and the diminution of contractility in the muscles after death. They all are found in a state of relaxation, incapable of being excited by their accustomed stimuli; and it has been further observed, that the body is disposed to run rapidly into a state of decomposition. These facts appear to identify, at least to a certain de gree, the property of muscular contraction with that of the coagulation of the fibrin, and this identity is further supported by considering that the chemical composition of fibrin is similar to that of muscle.(d) It has been suggested that perhaps the most obvious and consistent view of the subject is, that the fibrin or gluten has a natural disposition to assume the solid form when no circumstance prevents it from exercising this inherent tendency, as it is gradually added to the blood, particle by particle. While this fluid is in a state of agitation in the vessels, it has no opportunity of concreting, but when it is suffered to be at rest either within or without the vessels, it is then able to exercise its natural tendency.(e) In this respect the coagulation of the fibrin of the blood is very analogous to the formation of organized solids in general, which only exercise their property of concreting or coalescing under certain circumstances, and when those causes, either chemical or mechanical, which would tend to prevent the operation, are not in action.(f) Upon this principle it has been observed, that we should be induced to regard the coagulation of the blood as analogous rather to the operation by which the muscular fibre is originally formed, than to that by which its contractile power is afterwards occasionally called into action. This fibrin or gluten is the most essential part of the blood.(g) The 14. Proper principal property of this part of the blood, which constitutes the fibrin ties of or lymph or gluten, (besides that of continually nourishing and supplying fibrin or new materials to the frame in the ordinary course of its circulation,) is lymph. that of repairing injuries to the solids.(h) We have seen that by this fibrin, gluten, or lymph, fractured bones reunite, (i) and lacerated muscles, arteries, and veins, and even nerves, are reunited or reproduced.(k) It causes the reunion of divided parts: thus when two newly cut surfaces of flesh (even those which had not been previously connected) are laid in close opposition they will unite; and when the operation has been performed under the most favourable circumstances, the trace of the wound will be scarcely perceptible either to the eye, or in the structure, or in the performance of the useful operation of the original part. What will appear more wonderful is, that parts of different structures are capable of forming this close union; and even the coats or parts of arteries, veins, and nerves, become repaired and renovated; and even portions of the body, which had been entirely cut off from other parts of the same body, or even from a different body, if speedily applied to a recently divided surface, will unite by means of the fibrin or gluten, and renew and retain their original function.() Dr. Bostock observes, that though there is reason to believe that the fibrin is the intermedium by which the process is effected, yet that no rational method is known by which the successive steps of the operation (e) 1 Bost. 354; Hunter on Blood, 26. (d) Id. 238. (e) 1 Bost. 356. But if this position be true, how can it be reconciled with Dr. Davy's experiments, where the blood coagulates during agitation, a fact well established. (f) 1 Bost. 356.. (g) 1 Bell, Anat. 526, 527; 2 Horn. Anat. 179. (h) 1 Bost. 359, 362; J. Hunter's Trea (i) Ante, 21, 42, 43; 1 Bost. 100 to (7) 1 Boşt. 360; J. Hunter on Blood, 208, CHAP. V. BLOOD. 15. Of the red glo bules or can be explained. We may indeed conceive of the divided end of an artery which belongs to the cut surface nearest the heart discharging a portion of its fibrin, which may coagulate and form a basis, (or nidus, as it has been termed,) through which the current of blood may afterwards form a new channel; but in what way is this stream to discover the ends of the arteries of the other surface, and by what power is it to enter them, and how are these insulated parts to propel their blood into the veins, and how are the veins of the divided part to transmit their contents into the veins of the body? These are questions that at present we are not able to answer. (m) Sir Everard Home has stated that a quantity of carbonic acid is always present in the blood, and that during its coagulation this acid is extricated, and that by its extrication it forms linear passages or tubes in the substance of the blood, into which the vessels of contiguous parts are elongated, and which become the rudiments of future arteries, and that the serum is the nidus in which these tubes are formed, as they are said to be altogether independent of the globules which are supposed to be the more immediate constituents of the fibrin; but Dr. Bostock insists that as the formation of regular tubes could not be the result of the extrication of gas in a viscid fluid, therefore the formation of the tubes must be the result of a tendency in the fluid in question to assume an organic arrangement:(n) but it appears to be still a disputed point whether it is carbonic acid or azote, or some other gas, that occasions the formation of these tubes.(0) The second constituent of the crassamentum (after considering the fibrin) is the red particles or globules. When considering the subject of respiration, and its effect upon the blood, it has been observed that the particles. crassamentum itself is composed of fibrin and red particles, and the red globules are regarded as that part of the crassamentum on which the air more particularly acts. Their organization is peculiar to themselves, and they are the only parts of the blood which is known to possess any specific chemical characters; and we have reason to suppose that they are easily decomposed and are more readily acted upon than either the serum or the fibrin of the blood; and it is principally by their change of colour that we are enabled to form our judgment respecting the action of the air upon the blood. The nature of this action is, however, obscure, and we know nothing more than that they appear to have a strong attraction for oxygen; for although it has been shown that they contain a small quantity of iron, there appears, Dr. Bostock says, no foundation for the opinion that the iron is the part by which the oxygen is altered, nor is it the immediate cause of the red colour.(p) Great differences of opinion as to the form and size of these particles have existed,(7) and the composition and chemical properties of these bodies still remain the subject of controversy.(r) It seems established that some, though but a small quantity of iron is to be found in the globules of the blood, from which it is inferred it receives its red colour;(s) and it is supposed by some that it is the red particles of the crassamentum on which the air more particularly acts, and that the iron, however minute in quantity, is the agent by means of which the blood acts upon the atmosphere.(t) The quantity (m) 1 Bost. 360, 361. The blood of the entire living frame operates like sap from the stock of a tree, which oozes through the inoculated bud or engrafted cut, and thus assimilates the one with the other. (n) 1 Bost. 362; Phil. Trans. for A. D. 1818; p. 181, et seq. and A. D. 1820, p. 2. (0) 1 Bost. 362, note. (p) 2 Bost. 110 to 113, 478, 479. But 1 |