36 THE CONNECTIVE TISSUES [CH. IV. 



corpuscles called lymphocytes. It is found in the lymphatic glands, 

 the thymus, the tonsils, in the follicular glands of the tongue, in Peyer's 

 patches, and in the solitary glands of the intestines, in the Malpighian 

 corpuscles of the spleen, and under the epithelium of many mucous 

 membranes. 



Jelly-like Connective Tissue. 



We have now considered connective tissues in which fibres of one 

 or the other kind predominate, and some in which the cells are in 

 preponderance. We come lastly to a form of connective tissue in 

 which the ground -substance is in excess of the other histological 

 elements. This is called jelly-like connective tissue. The cells and 

 fibres scattered through it are few and far between. It is found 

 largely in the embryo, notably in the Whartonian jelly, which sur- 

 rounds and protects the blood-vessels of the umbilical cord. In the 

 adult it is found in the vitreous humour of the eye. 



The occurrence of large quantities of ground-substance in such 

 tissues has enabled physiologists to examine its chemical nature. 

 Its chief constituents are water, and one or more varieties of mucin- 

 like substances termed mucoids and mineral salts (especially sodium 

 chloride). 



