513 



BLOOD. 



BLOCD. 



511 



place. The globules darkened by carbonic acid become again florid in 

 oxygen, with disengagement of carbonic acid. The same thing takes 

 place in nitrous oxide. It is clear that they have here undergone no 

 decomposition, a:;d consequently they possess the power of combining 

 with gases, while the compound they form with carbonic acid is 

 destroyed by oxygen. When left to themselves out of the body, the 

 compound formed with oxygen again becomes dark, but does not 

 recover its florid colour a second time by the action of oxygen. The 

 globules of the blood contain a compound of iron. From the never- 

 failing presence of iron in red blood, we must conclude that it is unques- 

 tionably necessary to animal life ; and since physiology has proved 

 that the globules take no share in the process of nutrition, it cannot 

 be doubted that they play a part in the process of respiration. The 

 compound of iron in the globules has the characters of an oxidised 

 compound, for it is decomposed by sulphuretted hydrogen, exactly in 

 the same way as the oxidea or other analogous compounds of iron. 

 By means of diluted mineral acids, peroxide (sesqui-oxide) of iron 

 may be extracted at the ordinary temperature from the fresh or dried 

 red colouring matter of the blood. The characters of the compounds 

 of iron may perhaps assist us to explain the share which that metal 

 takes in the respiratory process. No other metal can be compared 

 with iron for the remarkable properties of its compounds. The com- 

 pounds of protoxide of iron possess the property of depriving other 

 oxidised compounds of oxygen ; while the compounds of peroxide of 

 iron under other circumstances give us oxygen with the utmost 

 facility. Hydrated peroxide of iron, in contact with organic matters 

 destitute of sulphur, is converted into carbonate of the protoxide. 

 Carbonate of protoxide of iron, in contact with water and oxygen, is 

 decomposed ; all the carbonic acid is given off, and by absorption of 

 oxygen it passes into the hydrated peroxide, which may again be 

 converted into a compound of the protoxide. Not only the oxides of 

 iron but also the cyanides of that metal exhibit similar properties. 

 Prussian blue contains iron in combination with all the organic ele- 

 ments of the body ; hydrogen and oxygen (water), carbon and nitrogen 

 (cyanogen). When it is exposed to light, cyanogen is given off, and it 

 becomes white ; in the dark it attracts oxygen, and recovers its blue 

 colour. All these observations taken together lead to the opinion that 

 the globules of arterial blood contain a compound of iron saturated 

 with oxygen, which in the living blood loses its oxygen during its 

 passage through the capillaries. The same thing occurs when it is 

 separated from the body and begins to undergo decomposition. The 

 compound, rich in oxygen, passes therefore, by the loss of oxygen, 

 into one far less charged with that element. One of the products of 

 oxidation formed in this process is carbonic acid. The compound of 

 iron in the venous blood possesses the property of combining with 

 carbonic acid ; and it is obvious that the globules of the arterial blood, 

 after losing a part of their oxygen, will, if they meet with carbonic 

 acid, combine with that substance. When they reach the lungs they 

 will again take up the oxygen they have lost ; for every volume of 

 oxygen absorbed, a corresponding volume of carbonic acid will lie 

 separated ; they will return to their former state, that is, they will 

 again acquire the power of giving off oxygen. For every volume of 

 oxygen which the globules can give off, there will be formed (as car- 

 bonic acid contains its own volume of oxygen without condensation) 

 neither more nor less than an equal volume of carbonic acid. For 

 every volume of oxygen which the globules are capable of absorbing, 

 no more carbonic acid can possibly be separated than that volume of 

 oxygen can produce. When carbonate of protoxide of iron by the 

 absorption of oxygen passes into the hydrated peroxide, there are 

 given off, for every volume of oxygen necessary to the change from 

 protoxide to peroxide of iron, four volumes of carbonic acid gas. But 

 from the one volume of oxygen only one volume of carbonic acid gas 

 can be produced. And the absorptioh of one volume of oxygen can 

 only cause directly the separation of an equal volume of carbonic 

 acid ; consequently the substance or compound which has lost its 

 oxygen during the passage of arterial into venous blood, must have 

 been capable of absorbing or combining with carbonic acid ; and we 

 find, in point of fact, that the living blood is never in any state satu- 

 rated with carbonic acid ; that it is capable of taking up an additional 

 quantity without any apparent disturbance of the functions of the 

 globules. Thus, for instance, after drinking effervescing wines, beer, 

 or mineral waters, more carbonic acid must necessarily be expired 

 than at other times. In all cases where the oxygen of the arterial 

 globules has been partly expended otherwise than in the formation of 

 carbonic acid, the amount of this latter gas expired will correspond 

 exactly with that which has been formed ; less however will be given 

 out after the use of fat and of still wines than after champagne. 

 According to the views now developed, the globules of arterial blood 

 in their passage through the capillaries yield oxygen to certain con- 

 stituents of the body. A small portion of this oxygen serves to pro- 

 duce the change of matter, and determines the separation of living 

 parts, and their conversion into lifeless compounds, as well as the 

 formation of tire scretions and excretions. The greater part, however, 

 of the oxygen is employed in converting into oxidised compounds tin- 

 newly-formed substances which no longer form part of the living 

 tissues. In their return towards the heart, the globules which have 

 lost their oxygen combine with carbonic acid, producing venous 

 blur .d ; ,md when they reach the lungs an exchange takes place between 



HAT. HIST. 1)IV. VOL. I. 



this carbonic acid and the oxygen of the atmosphere. The organic 

 compound of iron, which exists in venous blood, recovers in the lungs 

 the oxygen it has lost, and in consequence of this absorption of oxygen 

 the carbonic acid in combination with it is separated." 



Mulder is strongly opposed to this theory ; he denies that the iron 

 takes any essential part in the respiratory process ; and he refers the 

 process entirely to the oxidation of the protein-compounds. He 

 alleges the following grounds against the probability of the correct- 

 ness of Liebig's views : 



1. The iron is so intimately connected with the other elements of 

 hsematin, that it cannot be removed even by long digestion of this 

 constituent in dilute hydrochloric or sulphuric acid. If these re-ngents 

 cannot effect its oxidation, it is highly improbable that it should be 

 oxidised in the lungs. Respecting Liebig's assertion that dilute acids 

 remove iron from dried blood, Mulder proves that this fact is value- 

 less in relation to his theoiy, because other constituents of the blood 

 besides the hsematiu contain this metal, apparently in an oxidised 

 state. 



2. If, as Liebig asserts, peroxide of iron exists in arterial blood, 

 and carbonate of protoxide of iron in venous blood, almost any dilute 

 acid would be capable of removing it. But this is not the case. 

 Hffimatin properly prepared may be digested with dilute hydrochloric 

 or sulphuric acid for many days without the least diminution in the 

 quantity of the iron. From haematin treated in this manner Mulder 

 obtained by combustion 9'49 per cent, of peroxide of iron, which is 

 the constant quantity alwjiys left after the combustion of well- 

 prepared hxmatiu. 



3. The probability that the iron exists in a metallic state is strongly 

 supported by the observation that hydrogen is evolved when a clot of 

 blood is digested in sulphuric acid, and water is added. Mulder 

 suggests that it occurs as an integral constituent of hscmatiu in just 

 the same manner that iodine occurs in sponge, sulphur in cystin, or 

 arsenic in the cacodyl series. 



4. The amount of hscmatin in the whole mass of the blood is far 

 too inconsiderable to carry a due supply of oxygen to the whole 

 system. 



Having thus shown the principal objections to which Liebig's 

 celebrated theory is open, we shall endeavour briefly to explain the 

 rival theory of Mulder. It is a well-known fact, that the protein- 

 compounds are capable of undergoing oxidation when in contact with 

 the oxygen of the air. When a protein-compound becomes oxidised, 

 it assumes a plastic character, that is to say, it has a tendency to 

 become solid and to adhere to solid substances. It has been already 

 stated that the blood-corpuscles are cells, of which the wall consists 

 of a protein-compound named globulin. When a respiration is per- 

 formed, the exterior layer of such of the corpuscles as are exposed in 

 the lungs to the action of the air, becomes converted into oxidised 

 protein, it becomes whitish and less transparent. This is the state in 

 which the corpuscles exist in arterial blood. As they reach the 

 capillary system, this white exterior layer is employed in the change 

 of material of the body, and is in that way consumed. Having lost this 

 white layer, they again become transparent. The dark colouring 

 substance in the corpuscles of arterial blood, shining through a white 

 layer, must necessarily appear of a bright red tint, as may be shown. 

 by pouring dark red blood into a vessel of milky glass. 



The fluid part of the blood called the Serum is a transparent fluid, 

 of a light straw-colour tinged with green. The proportion of it to the 

 solid part of the blood, or Clot, differs in different species of animals. 

 There is a strict relation between its relative proportion and the 

 strength and ferocity, or weakness and gentleness of the animal. It 

 is small in proportion to the power and fierceness of the animal, and 

 large in proportion to its weakness and timidity : thus it is small in 

 the carnivorous animals, and large in the hare, sheep, and so on. 



Serum has an adhesive consistence and a saline taste. Its 

 characteristic property is that of coagulating by heat and by the 

 application of certain chemical agents. At the temperature of 

 160 it is converted into a white opaque solid substance, exactly 

 resembling the white of egg when hardened by boiling, being in fact 

 perfectly pure albumen. Serum contains a quantity of uncombined 

 alkali, for it converts the vegetable colours to green, and it holds in 

 solution various earthy and neutral salts. According to M. Le Canu, 

 who has made the most recent chemical analysis of serum, 1000 parts 

 contain 



Water ... .... 906-00 



Albumen 78'00 



Animal Matter soluble in water and alcohol . . 1'69 



Albumen combined with Soda 2"10 



Crystallisable Fatty Matter . . . . . 1'20 



Oily Matter I'OO 



Hydrochlorate of Soda and Potash .... C'OO 

 Subcarbonate and Phosphate of Soda and Sulphate 



of Potash . 2-10 



Phosphate of Lime, Magnesia, and Iron, with Suli- 



carbonate of Lime and Magnesia . '91 



Loss I'OO 



1000-00 



If a mass of coagulated Serum be cut into small pieces and placed in 



2 L 



