LIVING CONNECTIVE TISSUE CELLS 139 



ectoplasmic theory of Hansen does not satisfactorily account for 

 it and its elaboration by Mall is not as specific in this particular 

 as one might wish. These theories do not appear to fully har- 

 monize with the relatively active motion and locomotion of the 

 connective tissue cells which I have observed in the fins of living 

 fish and which Harrison, Burrows and others have also to some 

 extent recognized in tissue cultures. The cells are not suffi- 

 ciently quiescent to permit of endoplasmic retraction with deposit 

 of ectoplasmic fibers unless this retraction is rapidly performed, 

 in which case it should be observable in the living embryo. I 

 have in one or two cases suspected such a method of deposit but 

 have not as yet been able to convince myself that it actually occurs; 

 in fact I now doubt if it occurs at all. 



The ectoplasmic theory presupposes that the fibers arise at the 

 surface of the cell. This I have found to be not always the case. 

 The clear delineation of fibers by the Bielschowsky method makes 

 it possible to follow their course within the cell more carefully 

 than ever before and I find that the blackened fibrils within the 

 cell both in pig embryos (fig. 9) and in the fish's fin very frequently 

 pass close to the nucleus, sometimes ending almost in contact with 

 this structure, but more frequently passing by so closely as to be 

 in actual contact with the nuclear membrane. I am aware that 

 Golowinski using the iron haematoxylin method, demonstrated 

 the presence of fibers at the surface of the connective tissue cells 

 of the umbilical cord and that the apparent relation to the nu- 

 cleus was explained by him as due to obliquity of section. But I 

 have not in my preparations been able to convince myself of the 

 adequacy of this explanation. I have found fibers to be not 

 always at the surface of the cell, they may and frequent ty do pene- 

 trate entirely through the cytoplasm of the cell, as I have previ- 

 ously described 3 for mature reticular tissue. In the developing 

 connective tissue, as well as in reticular tissue, such penetration of 

 cells by the fibers is so frequent as to appear quite characteristic. 

 It seems to me that the intimate relation of connective tissue cells 

 and fibers in embryonic tissues can only be accounted for by tak- 



3 Loc. tit., see fig. 10, page 293. 



