46 . HANDBOOK OF PHYSIOLOGY. 



various directions, sometimes appearing to pass in a more or less circular 

 or spiral manner round a small gelatinous mass of changed white fibre. 

 The cells of areolar tissues are connective-tissue corpuscles. They con- 

 sist of several varieties: branched, flattened cells which connect with 

 each other; flattened cells which do not branch; plasma cells; wander- 

 ing cells from the blood ; and sometimes pigment cells, as in the choroid 

 of the eye. The various elements are held together by cement substance, 

 penetrated by irregular canals carrying lymph. 



^.Special Forms (a.) Gelatinous Tissue. 



Distribution. Gelatinous connective tissue forms the chief part of 

 the bodies of jelly-fish; it is found in many parts of the human embryo, 



Fig. 45. 



Fig. 46. 



Fig. 45. Mucous connective tissue from the umbilical cord. o. Cells; b. fibrils. 

 Fig. 46. Part of a section of a lymphatic gland, from which the corpuscles have been for the 

 most part removed, showing the adenoid reticulum. (Klein and Noble Smith.) 



but remains in the adult only in the vitreous humor of the eye. It may 

 be best seen in the last-named situation, in the " Whartonian jelly " of 

 the umbilical cord, and in the enamel organ of developing teeth. 



Structure. It consists of cells, which in the vitreous humor are 

 rounded, and in the jelly of the enamel organ are stellate, imbedded in 

 a soft jelly-like inter-cellular substance which forms the bulk of the 

 tissue, and which contains a considerable quantity of mucin. In the 

 umbilical cord, that part of the jelly immediately surrounding the stel- 

 late cells shows marks of obscure fibrillation (fig. 45). 



(b.) Adenoid, this is also called retiform, lymphoid or lymphatic tissue. 



Distribution. This variety of tissue makes up the stroma of the spleen 

 and lymphatic glands, and is found also in the thymus, in the tonsils, 

 in the follicular glands of the tongue, in Peyer's patches, and in the sol- 

 itary glands of the intestines, and in the mucous membranes generally. 



