CELLS IN CONNECTIVE TISSUE 69 



journal, Ehrlich published the first of his far-reaching investigations on 

 the effects of various anilin dyes upon protoplasm. He showed that the 

 plasma cells found near the vessels in the mesentery of the rat, when 

 stained with basic dyes, exhibit very coarsely granular protoplasm (Fig. 

 55, m). Further studies led him to separate these granular cells from the 

 other forms of plasma cells. He was inclined to believe that they arose 

 from over-nourished connective tissue cells, and accordingly named them 

 mast cells (Mastzellen), referring to the mast or acorns on which animals 

 are fattened (Arch. f. Physiol., 1879, pp. 166-171). In another com- 

 munication in the same volume (pp. 571-579), he introduced a further 

 subdivision of cells which may be alike in form but which react differ- 

 ently to the anilin dyes. In contrast with the basic granules of the mast 

 cells, which are not stained with the acid dye eosin, he found other granules 

 which stain deeply with eosin but do not respond to the basic dyes. 

 These granules are now generally known as eosinophilic, and the cells 

 which contain them are called eosinophiles. Mast cell granules are often 

 referred to as basophilic, but since some confusion results from calling 

 the entire cells basophiles, they are still known as mast cells. Cells of 

 both classes are found in the circulating blood, and will be described with 

 the blood corpuscles; both kinds are found also in the intercellular spaces 

 of connective tissue. It is known that various forms of blood corpuscles 

 develop in the reticular tissue of lymph glands and bone marrow, from 

 which they enter the blood vessels; and it is also very evident that cells 

 leave the vessels and enter the intercellular spaces of connective tissue. 

 There has been endless discussion as to whether the eosinophiles of con- 

 nective tissue and blood are the same sort of cell; and also whether the 

 "mast leucocytes" in the vessels and the mast cells in the surrounding 

 tissue are identical. Maximow states that there is no genetic relation 

 between mast cells and mast leucocytes in the adult, but "whether in 

 embryonic life they are likewise independent is still undecided." As to 

 the eosinophiles, he says: Those found in the connective tissue are 

 generally eosinophilic corpuscles which have emigrated from the vessels. 

 'Any proof of a local origin in connective tissue is lacking." But Weiden- 

 reich considers that eosinophilic granules are derived from broken-down red 

 corpuscles, which are taken up by white blood corpuscles and by con- 

 nective tissue cells, both of which become thereby eosinophilic. 



In ordinary sections of connective tissue, stained with haematoxylin 

 and eosin, eosinophiles are seldom overlooked, because of the brilliant 

 color of their granules. Mast cells, however, should be sought for in 

 tissue preserved either in formalin or alcohol, and stained with Unna's 

 polychrome methylene blue or some other basic dye. The preparation 

 shown in Fig. 55 is a portion of the mesentery preserved by being tied 

 across the end of a short glass tube and immersed in alcohol. The tissue 



