A PRELIMINARY NOTE OX THE RELATION OF NOR- 

 MAL LIVING CELLS TO THE EXISTING THEORIES OF 

 THE HISTOGENESIS OF CONNECTIVE TISSUE. 



JEREMIAH S. FERGUSON, M.S., M.D., 



ASSISTANT PROFESSOR OF HISTOLOGY, CORNELL UNIVERSITY 

 MEDICAL COLLEGE, NEW YORK CITY. 



The connective issue of the adult is in the embryo derived 

 from the mesenchyme. The same is true of certain other 

 tissues, endothelium, muscle, and cartilage, bone and dentine, 

 if these last be not included within the scope of the term con- 

 nective tissue. It is in this narrower sense that the term con- 

 nective tissue is herein used. 



In considering the origin of connective tissue one has to 

 take into account two distinct elements, cells and fibers. Of 

 the cells there are at various stages in the embryonic mesenchyme 

 three distinct types: (a) the wandering cells, viz., leucocytes, 

 which are more directly concerned with the processes of hse- 

 matopoiesis; (b) those cells which give rise to the true wandering 

 connective tissue cells of the mature tissues, the mast cells, 

 plasma cells, etc., \vhose history is more or less closely concerned 

 with that of the embryonic leucocytes; (c) those typical con- 

 nective tissue cells which are related to the fibers and which 

 are commonly known as the "fixed" connective tissue cells. 

 It is without doubt only the last type which is concerned with 

 the origin of the connective tissue fibers, hence the present note 

 deals only with this type of cell. 



At least two types of fibers have also to be considered as 

 arising in the connective tissue mesenchyme, the elastic and the 

 collaginous. We are here concerned only with the latter type, 

 for the reason that the elastic fibers arise at a later period; thus 

 the origin of the connective tissue libcr> concerns primarily 

 the collaginous, or so-called "white fillers." It is unnecessary 

 to distinguish at the early stage under consider.it ion between 



such varieties of collaginous fibers as "reticulum" and " librog- 



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