CONNECTIVE TISSUE CAETILAGE BONE 



FIG. 76. ADIPOSE TISSUE. 



The fat cells have been blackened by osmium 

 tetroxid. X 110. 



8, 2, 1914) fat cells 

 can arise also by a 

 process involving the 

 enclosure of free fat 

 spherules by endothe- 

 lial cells. They suggest 

 that fat cells may be 

 modified endothelial 

 rrlls rather than mod- 

 ified fibroblasts. 



The forerunners of 

 the original smallest 

 fat droplets are gran- 

 ules (Altmann, 1890). 

 In the subcutaneous 

 tissue of Myxine (Hag- 

 fish) embryos, Schrei- 



ner (Anat. Anz. 48, 7, 1915) has described the process of fat elaboration 



in minute detail. The pre-fat granules originate from rod-like chromidia 



('mitochondria') by process 



of segmentation. The chro- 

 midia arise as nucleolar buds 



which wander through the 



nucleus and traverse the nu- 

 clear membrane as spherical 



granules. These 'primary 



granules' elongate into rods, 



and subsequently segment into 



'secondary granules,' which 



liquefy and coalesce to form 



the definitive fat spherules. 



This important investigation 



suggests a functional role for 



mitochondria in terms of a 



nutritive material upon which 



FIG. 77. DEVELOPING ADIPOSE TISSUE FROM 

 THE SUBCUTANEOUS TISSUE OF AN INFANT. 



The fat has been removed by immersion in 

 alcohol and ether. The polygonal outlines of 

 the fat cells are well shown. Within many of 

 them is seen the finer cytoplasmic network by 

 which the inclosed droplets of fat were in- 

 vested; this network had not been completely 

 replaced by the accumulation of fat. Hema- 

 tein and eosin. Photo. X 325. 



cell metabolism and differen- 

 tiation may depend. 



Lymphoid Tissue (Ade- 

 noid Tissue}. Lymphoid tissue is a reticular tissue the meshes of whose 

 network are occupied by a closely packed mass of lymphocytes, cells with 



