MAST CELL IN EVOLUTION 



later in all the subcutaneous connective tissue. Staemmler (1921) emphasizes 

 the high mast-cell content of the developing thymus. Meanwhile, a generalized 

 metachromasia of the connective tisue is fading (Holmgren, 1939, 1940; 

 Bairati and Bianchini, 1953; Hjelmman, 1954; Kitanishi, 1956), although, as is 

 well known, metachromasia persists and is an outstanding feature of the 

 Wharton's jelly of the umbilical cord. 



Numerous investigators have studied the development and distribution of 

 mast cells in the umbilical cord, seeking a possible relationship between the 

 diffuse metachromasia of Wharton's jelly and the compact, granular meta- 

 chromasia of the mast cells (Lehner, 1924; Pescetto, 1950; Sundberg et ai 

 1954; Moore, 1956). Mast cells appear much later than the Wharton's jelly, 

 which is itself non-metachromatic when it is first laid down in utero: later the 

 two types of metachromasia — diffuse and granular — can be distinguished by 

 their differing reactivity to certain enzymes (Moore and Schoenberg, 1957a 

 and b). Schoenberg and Moore (1958) have recently suggested that a simple 

 carbohydrate precursor elaborated by the fibroblast undergoes further con- 

 struction in the tissue spaces, a type of extracellular synthesis now known to 

 occur around certain micro-organisms (Markowitz et al, 1958). I have suggested 

 that a final alteration and storage of high-molecular sulphated mucopoly- 

 saccharide occurs in the mast cell (Riley, 1954, 1955). This would accord with 

 the finding of Hopf (1952) that mast cells often become very numerous in the 

 stump of the cord and adjacent peri-umbilical skin during the immediate 

 neonatal period. At this time small mast cells, rather poor in granules, are 

 demonstrable at sites in which mature cells are found in later life (Audrey, 1896). 



In the adult, mast cells are common in all loose subcutaneous and sub- 

 mucous connective tissue (Harris, 1900; Staemmler, 1921). They occur 

 frequently in the connective tissue of the female breast (Higuchi, 1930) and in 

 the intermuscular connective tissue of uterus, bladder and even the tongue 

 (Raudnitz, 1883; Staemmler, 1921): indeed, they are common in the tongue of 

 most species (Westphal, 1891; Clowes and Owen, 1904). In the skin itself the 

 cells occur mainly near hair follicles, glands, small blood vessels (Ehrlich, 

 1878; Schwenter-Trachsler, 1906; Staemmler, 1921; Sylven, 1941) and between 

 fat cells (Hissard et al, 19506), tending, as Ehrlich so clearly pointed out in his 

 thesis (1878, trans, p. 87) 'to concentrate around the preformed structures 

 which traverse the connective tissue'. 



In the gut the mast cells are situated chiefly in the villi, around the necks of 

 the duodenal glands of Lieberkuhn and scattered throughout the submucosa 

 of the small intestine and caecum (Westphal, 1891; Hardy and Wesbrook, 

 1895; Sansonow, 1909). 



The perivascular habitat of the mast cell is so characteristic as to pass almost 

 without comment. Greggio (1911) and Quensel (1928) stress the presence of 



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