240 



DEVELOPMENT OF CONNECTIVE TISSUE. 



otherwise removed, as by a short treatment with dilute alkali, the fibres of the 

 reticulum come clearly into view (figs. 280, 281). The true structure of this tissue 

 was first pointed out by Bizzozero. 



In many situations the meshes of the retiform tissue are occupied by numerous 

 corpuscles which closely resemble the pale blood- or lymph-corpuscles, but have a 



Fig. 280. RETICULUM FROM THE MEDULLARY PART OP A LYMPHATIC GLAND. (E. A. S.) 



tr, end of a trabecula of fibrous tissue ; r, r, open reticulum of the lymph-path, continuous with the 

 fibrils of the trabecula ; r', r', denser reticulum of the medullary lymphoid cords. The cells of the 

 tissue are not represented, the figure being taken from a preparation in which only the connective tissue 

 fibrils and the reticulum are stained. 



relatively larger nucleus, and less protoplasm than those. They are known as 

 lymphoid cells, and the tissue containing them is termed lymphoid or adenoid 

 tissue. This tissue is found composing the greater part of the lymphatic glands, 



Fig. 281. END OP A FIBROUS TRABECULA 



FROM THE SAME PREPARATION, SHOWING 

 THE CONTINUITY OF THE CONNECTIVE 

 TISSUE FIBRILS WITH THE RETICULUM : 

 HIGHLY MAGNIFIED. (E. A. S. ) 



tr, trabecula ; r, reticulum. 



and other structures allied to them, 

 such as the solitary and agminated 

 glands of the intestine, and the simi- 

 lar structures in the tonsils and 

 elsewhere. Moreover, the alimentary 

 mucous membrane is in some parts 

 composed of the same tissue, and 

 it occurs also in other mucous mem- 

 branes and, in the form either of elon- 

 gated tracts or of isolated nodules, in many parts of the serous membranes. In the 

 spleen, the interstices of the retiform tissue are for the most part occupied by blood, 

 instead of by lymph as elsewhere. In organs into the construction of which this 

 tissue enters, it serves as a supporting framework to those parts of the organ into 

 which connective tissue of the ordinary kind does not penetrate. 



DEVELOPMENT OF CONNECTIVE TISSUE. 



Those parts of the early embryo in which connective tissue is subsequently to 

 be developed, are at first composed entirely of embryonic cells, to all appearance 

 similar to those which constitute the mesoblastic layer generally. It is, however, 

 believed by many authorities that in their origin the cells which form the connective 



