258 



OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



ing for the known fact of its being insensible except when those trunks are 

 injured. The physical and chemical characters of the oleaginous substances 



Fig. 50. 



Bloodvessels of Fat; 1, minute flattened fat-lobule, in which the vessels only are represented; 3, the 

 terminal artery ; 4, the primitive vein ; 5, the fat vesicles of one border of the lobule, separately represented 

 magnified 100 diameters ; 2, plan of the arrangement of the capillaries on the exterior of the vesicles 

 more highly magnified. 



contained within the fat-cells, have already been sufficiently described ( 37, 

 38). The Margarin, which is the principal solid constituent of Human fat, is 

 dissolved in the Olein, forming a thick oil, which remains fluid at the ordinary 

 temperature of the body, but congeals when cooled much below it. That this 

 oil does not escape from the fat-cells during life, may be attributed to the moist- 

 ening of their walls by the aqueous fluid circulating through their vessels ; but 

 we find that the contents of the fat-cells are taken back into the general current 

 of the circulation when the food does not afford an adequate supply for the pur- 

 poses of respiration ; and we may probably explain this by the alkalinity of the 

 blood, which enables it to exert a certain solvent power for oleaginous matter, 

 and which when the amount ordinarily present in the blood has been exhausted, 

 or nearly so, will be exercised upon the fat within the cells of adipose tissue, 

 and will draw it into the circulating current. 1 



249. The relative quantity of Fat contained in the bodies of different indi- 

 viduals, varies more than does that of any other tissue. If there be no inca- 

 pacity for the production of fat-cells, the amount of Adipose tissue generated 

 will depend upon the quantity of their appropriate pabulum that may be supplied; 

 and this is, in fact, the surplus of the oleaginous matter ingested in the food, or 

 formed from its other constituents, after the various demands made upon it by 

 the wants of the system in general ( 41, 42) have been supplied. Hence the 

 formation of fat will be promoted by the use of oleaginous food, by inactive 

 habits of life, and by warmth of the surrounding atmosphere ; and it is by atten- 

 tion to these indications, that the breeders of animals obtain the largest produc- 

 tion of fat in the shortest time. There appears to be, among some individuals, 



1 It has been shown by Prof. Matteucci, that fatty matters, suspended in water in a 

 state of fine division, on one side of a membranous septum, will pass through it endosmoti- 

 cally towards a weak alkaline solution on the other. (See his "Lectures on the Physical 

 Phenomena of Living Beings," Dr. Pereira's edition, p. Ill, Am. Ed. 



