CHAP. III.] ADIPOSE TISSUE AND FAT. 85 



and omen turn, in the appendices epiploicse, on the heart, in the 

 subcutaneous layer of areolar tissue, but especially that of the 

 abdomen, and of the mammary region, and in the cancelli and 

 canals of the bones forming the medulla. It never occurs in the 

 areolar tissue of the scrotum and penis, or of the nymphse, nor in 

 that between the rectum and bladder, nor along the median line 

 beneath the skin, nor in sundry other situations. 



Fat is found in the liver, and in the brain and nerves, and occa- 

 sionally in other organs. In these organs it is not enclosed in 

 vesicles of adipose membrane, but in the elementary parts of the 

 tissues themselves, as in the epithelium cells of the liver, and in 

 the tubes and globules of the nervous substance. 



Development of Adipose Tissue. The vesicles Fi s- 

 of the adipose tissue are originally furnished with 

 nuclei, with a central granule or nucleolus. The 

 nucleus is situated on the inner surface of the cell- 

 membrane, or, if this be thick, in its substance. 

 The nucleus is speedily absorbed, and never after- 

 wards appears. Thus it is probable that the ori- 



ri A fat-cell, to shew the 



ginal development-cell assumes a permanent form nucleus; from scuwann: 



c. The adipose mem- 

 m the adipose Vesicle. brane. <* The nucleus. 



Formation of Fat. Many facts prove that the elements of fat are 

 derived from the blood. All the most recent analyses of that fluid 

 assign to it a certain proportion of both the crystallizable and the 

 oily portion of the fat ; according to Lecanu, about four parts in 

 a thousand. In some instances, the fatty matter accumulates in 

 the blood ; cases of which have been recorded by Morgagni, Hew- 

 son, Marcet, Traill, and Babington. In such cases the serum is 

 opaque and nearly as white as milk, and, on standing a short time, 

 a film forms on the surface like cream. On the addition of ether, 

 the creamy pellicle is dissolved, and the serum loses its opacity. 

 M. Blainville relates, that, in dissecting the last elephant that died 

 at the Jardin des Plantes, he happened to wound the jugular 

 vein, and the next morning he found that the stream of blood, 

 which flowed from the vein, had deposited on each side a consider- 

 able quantity of a fine fatty matter, which on analysis he found to 

 have exactly the composition of ordinary fat. 



From what source is this fatty material furnished to the blood? 

 From fatty matters introduced into the system in the food, whether 

 in animal or vegetable substances ; probably, also, from those parts 

 of the food which, in composition, resemble fat most nearly, such as 

 the non-nitrogenised articles of diet, starch, gum, sugar, alcohol, 



