It consequently follows from clinical and morphological researches, as well as from the observations on inflammatory processes, that the lymphocytes are in no way connected with the polynuclear leucocytes. We shall reach the same result in another way in the following section.
(γ) The Bone-marrow.
The spleen and lymphatic glands were at first regarded as the sole places of formation of the blood corpuscles. The almost simultaneous researches of Neumann and Bizzozero first attracted general attention to the importance of the bone-marrow. These authors showed that the early stages of the red blood corpuscles are produced there; a discovery which was quickly and generally recognised, and which soon became pathologically useful through the observations of Cohnheim and others. In this connection the observation was of great value, that after severe loss of blood the fatty marrow of the larger hollow bones again changes to red marrow, as it is evidence of the increased demands on the regenerative function of the bone-marrow.
We are unaware of a second place of formation of the red blood corpuscles in man. In other mammalia however, as we have above mentioned (see page 99), the spleen may also take a small share in the production of erythrocytes. The type which the normal blood formation follows in adults, and the deviations therefrom shewn in pernicious anæmia, have been described in the chapter on the red blood corpuscles. Ehrlich's view that the blood formation in pernicious anæmia belongs to a different type, which is analogous to the embyronic, was also described there.
In this section we have therefore to deal chiefly with the white blood corpuscles and their connection with the bone-marrow. In man as in a large number of animals (for example the monkey, guinea-pig, rabbit, pigeon and so forth) the bone-marrow exhibits the peculiarity that the cells it produces bear a specific granulation, in sharp contrast to the lymphatic glandular system, which contains elements free from granules, in the whole animal series.
The granulated cells of the bone-marrow fall into two groups.
The first group of the cells with "special granules" is very important since it constitutes a characteristic for certain species of animals. According to the class of animal they shew different tinctorial and morphological properties. Man and monkey for example have neutrophil granulation; guinea-pig and rabbit the pseudo-eosinophil granulation described by Kurloff; in birds we find two specific granulations present side by side, which both are oxyphil, and of which one is imbedded in the protoplasm in crystalline form, the other in the form of granules.
The kinds of special granulations so far investigated have the common property, that they stain in acid and neutral dyes respectively; they shew a much smaller affinity for the basic dyes. The fact that they greatly exceed the other elements of the bone-marrow in all classes of animals, is evidence of the importance of these granules.
The second group of bone-marrow cells contains granules which we find in the whole vertebrate series from the frog to man, and which therefore are not characteristic for any one species of animal. They are, (1) the eosinophil cells, (2) the basophil mast cells.
The bone-marrow forms which are free from granules consist mostly of mononuclear cells of different type. They are not nearly so numerous, or so important as the granulated kind, more especially as the first and predominant group.