g STRUCTURE OF BONE. 



him of breath for some time, and leave him gasping and speechless on the ground ; while a 

 tolerably severe blow in that region causes instantaneous death. 



Anxiety seems to fix its gnawing teeth chiefly in the solar plexus, causing indigestion and 

 many other similar maladies, and deranging the system so thoroughly that even after the 

 exciting cause is removed the effects are painf ully evident for many a sad year. 



By means of this complicated system of nerves the entire body, with its vital organs, is 

 permeated in every part by the animating power that gives vitality and energy to the frame 

 so long as the spirit abides therein. 



This is the portion of the nervous system that never slumbers nor sleeps, knowing no rest, 

 and never ceasing from its labors until the time comes when the spirit finally withdraws from 

 the material temple in which it has been enshrined. It is the very citadel of the nerve forces, 

 and is the last stronghold that yields to the conquering powers of death and decay. 



Thus it will be seen that each animal is a complex of many animals, interwoven with each 

 other, and mutually aiding each other. In the human body there is, for example, the nerve- 

 man, which has just been described ; there is a blood -man, which, if separated from the other 

 part of the body, is found to present a human form, perfect in proportions, and composed of 

 large trunk-vessels, dividing into smaller branches, until they terminate in their capillaries. 

 A rough preparation ot the blood-being may be made by filling the vessels with wax, and 

 dissolving away the remaining substances, thus leaving a waxen model of the arteries and 

 veins with their larger capillaries. 



Again, there is the fibrous and muscular man, composed of forms more massive and solid 

 than those which we have already examined. 



Lastly, there is the bone-man, which is the least developed of the human images, and 

 which, when stripped of the softer coverings, stands dense, dry, and lifeless ; the grim 

 scaffolding of the human edifice. Although the bones are not in themselves very pleasing 

 objects, yet their mode of arrangement, their adaptation to the wants of the animal whose 

 frame they support, and the beautiful mechanism of their construction, as revealed by the 

 microscope, give a spirit and a life, even to the study of dry bones. 



The larger hollows are caused by the minute blood-vessels which penetrate the bone 

 throughout its substance, and serve to deposit new particles, and to remove those whose work 

 is over. They are, in fact, a kind of lungs of the bones, through which the osseous system is 

 regenerated in a manner analogous to the respiration which regenerates the blood. In order 

 to supply a sufficient volume of blood to these various vessels, several trunk vessels enter the 

 bones at different parts of their form, and ramify out into innumerable branchlets, which 

 again separate into the hair-like vessels that pass through the above-mentioned canals. These 

 are termed, from their discoverer, C. Havers, the Haversian canals, and their shape and com- 

 parative size are most important in determining the class of beings which furnished the portion 

 of bone under examination. 



In the human bone these canals run so uniformly, that their cut diameters always afford 

 a roundish outline. But in the bird -bone, the Haversian canals frequently turn off abruptly 

 from their course, and running for a short distance at right angles, again dip and resume 

 their former direction. 



The reptiles possess very few Haversian canals, which, when they exist, are extremely 

 large, and devoid of that beautiful regularity which is so conspicuous in the mammalia, and 

 to a degree in the birds. 



The fish-bone is often totally destitute of these canals, while, in other cases, the bone is 

 thickly pierced with them, and exhibits also a number of minute tubes, white and delicate, 

 as if made of ivory. 



Returning to the human bone, the Haversian canals are seen to be surrounded with a 

 number of concentric bony rings, varying much in number and shape, on which are placed 

 sundry little black objects that somewhat resemble ants or similar insects. These latter 

 objects are known by the name of bone-cells ; and the little dark lines that radiate from them 

 are the indications of very minute tubes, the number and comparative dimensions of which 

 are extremely various in different animals. 



