Archive image from page 939 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana03todd Year: 1847 850 OSSEOUS TISSUE. have to be considered in relation to their num- ber, their size, and the parts which they contain. The number of canals in a given space is perhaps a little variable, but this variation will be regulated in some degree by the situation of the bone, but more especially by the age of the bone. Thus the transverse section of the femur of a human foetus of seven months will present many more canals than a section of equal mea- surement from the
Archive image from page 939 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana03todd Year: 1847 850 OSSEOUS TISSUE. have to be considered in relation to their num- ber, their size, and the parts which they contain. The number of canals in a given space is perhaps a little variable, but this variation will be regulated in some degree by the situation of the bone, but more especially by the age of the bone. Thus the transverse section of the femur of a human foetus of seven months will present many more canals than a section of equal mea- surement from the femur of an adult. In certain fish of which the Scarus is a spe- cimen, the Haversian canals are extremely nu- merous, so that bone cells become unnecessary, for here we find very few indeed, and in some sections none, (fig- 451.) Fig. 451. Section of bone from the Scarus, showing that where the Haversian canals are very numerous the bone cells are absent. The size of the Haversian canals takes a con- siderable range, varying from the 3J3rd to the sjLth of an inch, as stated by Mr. Smee. In the young subject they seem larger than in the old. But by far the most marked difference in size of these canals is to be observed in the antlers of the stag at different periods of their growth. At an early period of the existence of the antler, the vascular canals are large and numerous, while at the time of their completion in size the canals are less numerous in an equal space, and very small: indeed many seem all but obliterated. The density of bone is pro- duced more by the small size of the canals than by their comparative infrequency, though un- doubtedly they are less frequent in the compact bone, as that composing the shafts of long bones. In tracing individual canals, it will be found that the majority maintain the same size as far as we can follow them. This is not, however, observable in all. If a large canal be taken where it first enters the substance of the bone, it ma
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