Mulder is strongly opposed to this theory ; he denies that the iron takes any essential part in the respiratory process; and be 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 hamatin, that it cannot be removed even by long digestion of this constituent in dilute hydrochloric or sulphuric acid. If these re-agents 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 theory, because other constituents of the blood besides the hamatin 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. Hamatiu 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 hamatin treated in this manner Mulder obtained by combustion 9'49 per cent. of peroxide of iron, which is the constant quantity always left after the combustion of well. prepared hamatin.
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 hamatin in just the same manner that iodine occurs in sponge, sulphur in cystin, or arsenic in the cacodyl series.
4. The amount of hrematin 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-componud 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 ch‘nge 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— If a mass of coagulated Scrum be cut into small pieces and placed in the mouth of a funnel, a thin fluid drain. from it, which is called Seroaity, and which constitutes the gravy of meat dressed for the table.
According to M. Lo Cann the relative proportions of the consti tuents of Human Blood to each other, as they exist in most individuals, is as follows, this table being tho mean of two analyses:— 1000 parts of Human Blood contain— Water 78317 Fibrin . ..... . . Albumen 67/5 Colouring Matter,' . 126'31Fatty Matters in various states . . . . 5-16 Various undefined Animal Matters and Salts . . I 000'00 The relative proportion of the different constituents of the blood is constantly varying. Thus the quantity of water, according toll. Le Cann, is capable of varying in 1000 parts from the maximmt, to the minimum. In the male the medium quantity is 791'944, in the female 821'764 : the watery proportion also varies with tho temperament. In the lymphatic temperament, in the male it is in the female 803'716; while in the sanguineous it is., in the male 786'584, and in the female it is 793-007.