270 



OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



Fig. 63. 



external surface of the bone ; and these seem to derive their nutriment either 

 from the periosteum, or from the membrane lining the central medullary cavity; 

 according as they are nearest to one or to the other. The membranous lining of 

 the canals of Bone appears to be supplied with lymphatics, and also with nerves ; 

 but with both in a very limited amount. The periosteum seems to be scarcely 

 (if at all) sensible in the state of health, although painfully so when inflamed; 

 and the same may be said of the membrane lining the Haversian canals and 

 cancelli. The membrane lining the central medullary cavity, however, is more 

 sensitive ; since unequivocal signs of pain are manifested by an animal, when, 

 a bone having been sawn across, a probe is passed up the cavity, or an acrid 

 fluid is injected into it. 



260. When a Bone is subjected to the action of dilute nitric or muriatic acid, 

 which dissolves away the calcareous matter, a substance is left which possesses con- 

 siderable tenacity, but which is at the same time very flexible. This is commonly 

 termed Cartilage ; but the name is inappropriate, since it has neither the structure 

 nor the chemical composition of that tissue. The animal basis of Bone is not clion- 

 drin, the characteristic principle of Cartilage ( 34); but glutin y the organic compo- 

 nent of the White Fibrous tissue ( 33). When "examined microscopically, it 

 does not exhibit any cartilage-cells, but presents the laminated texture of the 

 original bone ; and the lacunae are still apparent, although their canaliculi cannot 



be readily traced. When a very thin lamella is peeled 

 off the surface of the bone, it is found to have a dis- 

 tinctly fibrous structure ; being composed, as was first 

 pointed out by Dr. Sharpey, 1 of fibres in all essential 

 respects resembling those of the White Fibrous tissue, 

 which decussate one another obliquely, so as to form 

 an exceedingly fine network, apparently adhering to 

 each other at the points of intersection (Fig. 63). The 

 minute apertures between the reticulated fibres seein to 

 give passage to the canaliculi. If very thin sections 

 of unaltered Bone, however, be examined with a high 

 power, the solid portion lying between the lacunae and 

 the canaliculi presents somewhat of a granular appear- 

 ance ; the granules, as stated by Mr. Tomes, 2 are often 

 distinctly visible without any artificial preparation, in 

 the substance of the delicate spicules of the cancelli, 

 when they are viewed with a high power ; and are made 

 very evident by a prolonged boiling in a Papin's di- 

 gester. They vary in diameter from l-6000th to 

 l-14,000th of an inch ; their shape is oval or oblong, 

 often angular; and they cohere firmly together, possi- 

 bly by the medium of some different material. Their 

 own substance appears to be perfectly homogeneous; 

 but it is made up of several components, as is demonstrated by Chemical analysis. 

 It appears certain, however, that the mineral matters must be intimately united 

 with the organized tissue, and not merely deposited in its interstices ; since no 

 distinction can be seen between them, even under the highest magnifying 

 powers. 



261. When the Calcareous matter of Bone has been removed by the action of 

 an acid, the Animal substance which remains is almost entirely dissolved by a 

 short boiling in water ; yielding to it a large quantity of Glutin. This, indeed, 



1 See his excellent account of the structure and development of Bone, in his Introduc- 

 tion to " Quain's Elements of Anatomy," p. 80, vol. i., Am. Ed. 



2 Todd and Bowman's "Physiological Anatomy," p. 112, Am. Ed., and "Cyclopedia of 

 Anatomy and Physiology," art. "Osseous Tissue." 



Thin layer peeled off a soft- 

 ened bone, as it appears under 

 a magnifying power of 400. The 

 figure, which is intended to re- 

 present the reticular structure 

 of a lamella, gives a better idea 

 of the object when held rather 

 farther off than usual from the 

 eye. 



