298 BLOOD AND BLOOD EXAMINATION 



Another variety of the white blood-corpuscles is the mast-cell (XI, a, b, c), 

 the peculiarities of which cannot be recognized in fresh blood, but only upon 

 the use of very definite methods of staining. [Mast-cells are beautifully 

 stained by the Eomanowsky method mentioned above. — Ed.] These cells are 

 characterized by a quite coarse, often irregular, granulation which as a rule 

 only partly fills up the protoplasm. Their distinctive feature, however, is 

 the basophilic reaction of the granulations and their power to modify the 

 color tone of most of the substances that stain them ("metachromasia"), so 

 that, for example, with kresyl-violet E they stain almost pure brown. They 

 also differ from other granulations by their ready solubility in water, so that 

 they can only be stained in alcoholic, not in watery, stain solutions. There- 

 fore, the two staining mixtures mentioned above which are in most common 

 use are not suitable for staining the granulations of the mast-cells, but we 

 can best use for this purpose alcoholic solutions of methylene-blue, dahlia, or 

 kresyl-violet E. [See last note. — Ed.J In the preparations stained with 

 triacid the mast-cells are recognizable, since the insufficient staining of the 

 granulation causes the cell to appear as if permeated by vacuoles (XI, c). 

 They are frequently so sparse in normal blood that they can only be discov- 

 ered by examining several preparations. 



These various cell forms may be determined in all normal blood by the 

 aid of different stains, and in the adult they are found in about the propor- 

 tion shown in the last division of Table A, where the large mononuclear 

 leukocytes and the transitional forms, on account of their close relationship, 

 are included in one group. 



In the arrangement of Table A the fact is disclosed that the lymphocytes 

 occupy a unique position among all the white blood-corpuscles. This is 

 mainly due to their origin : They originate in the lymphatic tisgue of the 

 body, the principal mass of which consists of the lymph-glands ; lesser amounts 

 of this variety of tissue are, however, also present in the bone-marrow, and it 

 therefore, perhaps, contributes a small portion of the lymphocytes of the blood. 

 The groups from the second to the fifth, however, originate exclusively in the 

 bone-marrow; only under definite pathological conditions does the production 

 of these varieties of cells also occur in other regions. The point of origin 

 of the mast-cells, which is chiefly in the bone-marrow, must also be the con- 

 nective tissue where they are formed in large quantities, particularly in certain 

 pathological conditions. 



A second comprehensive difference between the lymphocytes and the five 

 other varieties of cells consists in the fact that the latter have the property 

 of active movement which the lymphocytes do not possess ; we shall see later 

 that this difference is of great importance for the conception of pathological 

 processes. [It has been conclusively shown, I think, that lymphocytes do 

 possess the power of ameboid movement. — Ed.J 



