A system of practical medicine. By American authors. Vol. 1

by Unknown

Another feature in the absorption of extravasated blood is to be found on examination of the nearest chain of lymphatic glands. These may be seen swollen, of a dark-red color, and homogeneous surface. In density and color, as well as shape, they suggest the small supplementary spleens so frequently met with. These glands owe their change in appearance to the presence of large numbers of unaltered red blood-corpuscles which have entered the lymphatics traversing the region of hemorrhage. Within the lymph-glands they undergo a metamorphosis similar to that taking place at the part from which they were transferred. In the course of weeks or months there remains in the place of extravasation simply pigment, either as crystals or granules. Such pigment may remain for years imbedded within the tissues, or it may become absorbed, no trace of the original disturbance remaining. Its removal may take place presumably through a local solution of the pigment or the transfer of the granules or crystals by means of wandering cells to the nearest lymphatic glands or to the more remote parts of the body. An eventual elimination may occur through the secretions, especially the urine or bile, or there may result a deposition and permanent retention of the granules.

The investigations of Langhans are especially interesting, as suggesting efficient means for the production of pigment by cells whose function is intimately connected with pigmentation, as the cells of the rete Malpighii, of the choroid, and of certain tumors. The observations of Gussenbauer,⁴⁴ however, lead to the conclusion earlier advanced by Virchow, that pigment may be produced by the diffusion into cells, outside the vessels, of a solution of the pigment of the blood in the plasma of the latter. A precipitation of this dissolved pigment into granules is considered as eventually taking place.

⁴⁴ Ibid., 1875, lxiii. 322.

The method of origin of pigment thus described applies only to those discolorations which are unquestionably due to the metamorphosis of the coloring matter of the blood. Examples are furnished not only by the extravasation of blood on a large scale, but also by the escape of red blood-corpuscles in small numbers. Such an escape takes place from the pulmonary vessels in chronic obstruction to the admission of blood into the left side of the heart. The resulting brown induration of the lungs owes its color to the metamorphosed blood-pigment which is present as hæmatoidin in the interstitial tissue of the lungs, as well as contained within amoeboid cells in the alveolar and bronchial cavities.

It is probable that a similar transformation of hæmoglobin takes place in the spleen and elsewhere in melanæmia. In this condition the black granules of pigment, although differing in color and form from hæmatoidin, contain iron, and have received the name melanin. These granules are either free in the blood or are contained within the white blood-corpuscles. Their origin in the spleen is directly suggested by their frequent presence, often in considerable numbers, in the large, so-called splenic, corpuscles of the blood in the hepatic capillaries. Eventually, the pigment is found at more remote points in the circulation, and becomes fixed in the interstitial tissue of the various organs of the body.

The black pigment of the cells of melanotic tumors, also called melanin, is not to be directly traced to the hæmoglobin. Virchow⁴⁵ early called attention to the absence of iron in such pigment. Ferrated and non-ferrated varieties of melanin are thus to be recognized, the term being used in the same way as hæmatoidin, indicative of a microscopical appearance. A still further complication in the composition of melanin is suggested by Kunkel,⁴⁶ who has isolated a ferrated pigment from melanotic tumors. It shows, however, with the spectroscope, no relation to hæmatin, bilirubin, or hydrobilirubin. That its nature is similar to the normal pigment of the skin and choroid is suggested by the customary origin of the melanotic tumors in such pigmented tissues, and by the resemblance in appearance and reactions.

⁴⁵ Virchow's Archiv, 1847, i. 378.

⁴⁶ Ziegler, op. cit., 100.

That pigment of the most varied sort may be introduced into the body from without, and may remain indefinitely in the organism, is sufficiently well known from the results of tattooing. What is essential in such cases is, that the pigment shall be finely divided and insoluble in the fluids of the body. The most important of such pigmentations are those taking place through inhalation into the lungs. The reception by this channel of particles of soot is so common that it is most exceptional for the lungs of an adult to be free from the bluish-black discoloration due to this agent. Particles of coal-dust presenting the details of vegetable structure are met with in the lungs of individuals exposed to an atmosphere charged with this material. The worker compelled to inhale the dust of iron eventually accumulates a store of this substance, the quantity of which is essentially dependent upon the length of exposure, the degree of impregnation of the atmosphere, and the insufficient nature of the protectives employed.

Although a large part of the pigmentation under such circumstances is due to the direct presence of the foreign body, the appearances are also partly the result of consequent minute hemorrhages. The coal-dust and the iron-filings are often sharp and jagged fragments, which penetrate the delicate tissues, and the escaping red blood-corpuscles are acted upon by the amoeboid cells in the air-passages, with the consequent formation of hæmatin or hæmatoidin, as are the blood-corpuscles in larger hemorrhages. The inhaled pigment finds its way, either directly or by the agency of amoeboid cells, into the lymphatics and fibrous tissue of the lungs, and remains indefinitely either in the bronchial and pulmonary lymphatic glands or in the interstitial tissue of the lungs.