THE CONNECTIVE TISSUES. 43 



protoplasm into the white fibrillae, the periphery of the cell-body 

 becoming the fibres. While such conversion certainly occurs as a 

 primary process (Hemming), 'it is probable that the indirect mode, 

 whereby the fibres originate within an indifferent matrix, also con- 

 tributes to the production of fibrous tissue ; likewise that the young 

 fibres increase in size by independent growth. Regarding the de- 

 velopment of the elastic fibres, strong evidence supports the 

 view that the fibres are produced by the fusion of longitudinally- 

 disposed rows of minute particles, which appear within the indiffer- 

 ent intercellular matrix as the derivatives of the cells. 



Adipose tissue must be regarded as a member of the group of 

 connective substances, since the accumulation of oily matters within 

 the protoplasm of connective-tissue cells is responsible for the highly 



FIG. 48. 



Fat-cells embedded in subcutaneous areolar tissue : f, fat-cells ; n, nucleus ; c, 

 connective-tissue corpuscles ; iv, migratory cells ; e, elastic fibres ; b, capillary 

 blood-vessel. 



characteristic appearance of the tissue. Whether the fat-cells are 

 developed from elements especially set apart for this role, or whether 

 they are but modjfied orgUoaiy connective- tissue cells, is still a dis- 

 puted point ; there are, however, strong reasons for holding the latter 

 view as correct. 



Examined after the usual preparatory manipulations, and in places 

 where the cells maintain their individual forms, as in the omentum, 

 adipose tissue is seen to be made up of relatively large, clear, oval 

 or spherical sacs. The transparent contents are limited by a delicate 

 envelope, composed of cell-membrane and an extremely thin layer 

 of protoplasm ; on one sjgle of the sac a local accumulation marks 

 the position of the nucleus. 



Fat-cells occur usually in groups, supported and held together by 

 areolar tissue, through which ramifies a rich, vascular net-work. In 

 localities possessing considerable masses of adipose tissue, as beneath 

 the scalp and the skin, the cells are grouped into lobules, and these 



