66 



CONNECTIVE TISSUES ADIPOSE TISSUE. 



Yellow or Elastic Fibrous Tissue, from ligamentuui 

 nuchce. 



ous, form only a small part of the general mass. When examined under the 

 microscope, it is found to consist either of separate fibres, of bundles of fibres, 



or of broad membranous bauds of a 



FIG. 25. highly refractile and elastic sub- 



stance. The fibres vary indefinitely 

 in size, but have sharply-defined 

 dark borders, and appear to be ab- 

 ruptly broken ofFat their extremities. 

 They may anastomose and branch, 

 and where the fibres are broad and 

 membrauiform, and the anastomoses 

 close, a thin tissue results, as in the 

 lining or feuestrated membrane of 

 the arteries, which presents a con- 

 tinuous sheet with only here and 

 there minute holes or spaces. The 

 arrangement of its bloodvessels and 

 nerves, which are very few in num- 

 ber, is not accurately known. The fibres are reddened with Millou's re- 

 agent, and give the xanthoproteinic reaction. When long boiled, they 

 yield a little modified gelatin. Elastic tissue fulfils important functions in 

 the vascular system to which attention will hereafter be called and it 

 frequently occurs in situations where its physical properties enable muscular 

 tissue to be dispensed with, as in the ligameutum nuchre of the larger quad- 

 rupeds. Occasionally, though more rarely, it appears as the antagonist of 

 muscular effort, as in the chordae vocales, and typically in the hinge of the 

 conchifera. 



46. ADIPOSE TISSUE. This form of tissue is extensively distributed 

 through the animal kingdom, and consists of large cells filled with oil, 

 which in good specimens are individually separated from one another, as 

 well as collected into lobules by delicate trabecuhTe of connective tissue 

 (Fig. 26). It is more freely supplied with blood than most of the other 

 forms of cellular or connective tissue. The cells, though varying much in 

 size, average the -5 J^th of an inch in diameter, and are rendered polygonal 

 by mutual pressure; they are composed of a cell-wall of considerable thick- 

 ness, lined by a layer of protoplasm, in which an eci-entric nucleus with 



several nucleoli is imbedded, and which surrounds 

 a clear, perfectly transparent, and highly refrac- 

 tile drop of oil. The connective tissue uniting 

 the lobules is sometimes small in quantity, and 

 exceedingly delicate, as in the fat that surrounds 

 the kidney, and in the marrow of bones ; whilst in 

 other instances, as in the subcutaneous layer of 

 fat, it is possessed of much firmness, and is very 

 dense. No nerves have been discovered to termi- 

 nate in fat, nor do any lymphatics appear to take 

 origin in it. Adipose tissue is absent in the brain, 

 lungs, liver, and in the delicate skin of the eye- 

 lids, of the prepuce, scrotum, and ny in pine. In 

 all these regions, however, oily globules may be 

 seen on making fine sections. The absolute amount 



of fat in a well-nourished man amounts to about o^th of the weight of the 

 body. Infancy, mid-age, warmth, abundant food, especially of a saccharine 

 or oleaginous nature, freedom from mental anxiety, castration, indolent 

 habits, and inherited constitutional peculiarities, are all circumstances pre- 



FIG. 26. 



Four fat-cells, with intervening 

 connective tissues. 



