40 



GENERAL ANATOMY. 



ligaments of the larynx, the longitudinal elastic fibres of the trachea, the elastic 

 layer of the middle coat of the arteries, and in quadrupeds the ligamentum 

 nuchae. 



Free cells are found in the areolar tissue, as indicated above. The chief 

 forms are the spindle-shaped and the stellate, but numerous intermediate forms 

 are described by recent observers ; and of late much interest has been excited 

 by Von Eecklingshausen's discovery in the cellular tissue of cold-blooded ani- 

 mals of " wandering cells," or cells endowed with the power of automatic mo- 

 tion, and of changing their shape. These cells appear identical with the white 

 globules of the blood ; and it would seem from the researches of Strieker, Cohn- 

 heim, and others, that the walls of the capillary vessels are permeable to the 

 latter bodies, which are thus allowed to escape into the cellular tissue, there 

 to undergo development, normally into the natural cells and cellular tissue, or 

 abnormally into the corpuscular forms of lymph and pus, according to circum- 

 stances. 1 



ADIPOSE TISSUE. 



The common cellular membrane contains a variable quantity of Adipose 

 Tissue. The tissue is found also in various parts of the viscera as the mesen- 

 tery, the surface of the heart, &c., and fat enters largely into the formation of 

 the marrow of the bones. There is, however, a difference which should be 

 attended to between mere fat and adipose tissue. Adipose tissue consists of a 

 number of vesicles formed by an extremely delicate structureless membrane, 

 round or spherical where they have not been subject to pressure ; otherwise, 

 variously flattened. They are supplied and held together by capillary blood- 

 vessels (Fig. 11), and fine connective tissue, and each vesicle is filled with fat. 



[Fig. ll. 



Bloodvessels of fat. 1. Minute flattened fat-lobule, in which the vessels only are represented. 3. Terminal 

 artery. 4. Primitive vein. 5. Fat-cells of one border of the globule separately represented. (Magnified 

 100 diameters.) 2. Plan of arrangement of capillaries on exterior of fat-ceils, more highly magnified.] 



Fat is an unorganized substance, consisting of liquid oily matter (glycerine) 

 in combination with certain fatty acids, stearic, margaric, and elaic. Sometimes 

 the acids separate spontaneously before the fat is examined, and are seen under 

 the microscope in a crystalline form, as in the figure. By boiling the tissue in 



1 On this subject reference may be made to Von Recklingshausen, in Virchow's Arcluy. 

 Bd. xxviii., and Rollett in Strieker's Leh re von den Geweben, chap, ii., where the reader will 

 find references to Strieker, Cohnheim, Kiihne, and others. 



