

44 THE NORTHERN MICROSCOPIST. 


when wounded—in amputations are sometimes plugged, to stop the flow. 
When bones are deprived of their periosteum, they frequently exfoliate or 
throw off plates of diseased bone, or may become necrosed or dead. The 
medullary canals of adult long bones contain marrow as well as the cancellous 
tissue, likewise the Haversian canals in young bones; it is a transparent reddish 
fluid, in the long bones of adults it is yellow and fatty. 
Bone is developed at a very early period; the spine and cranial bones are 
first developed. At first, the parts destined to become bone consist of a 
congeries of cells connected together by an amorphous blastema, which consti- 
tutes the simplest form of cartilage ; this assumes a complete miniature of the 
form of bone.it is destined to lay the foundation for, in fact zs a temporary 
cartilage, which in due time becomes converted into bone, and as ossification is 
a slow process and not completed until adult life, it grows in size by interstis- 
itical development of new cells. ‘The ossification of this temporary cartilage 
commences at certain points or centres from which the process extends into the 
surrounding substance. In the fifth to seventh week the bones commence 
growing in the embryo ; first, in the clavicle or lower jaw, then the vertebra 
humerus femur ribs and cartilaginous portion of occipital bone. I think 
it scarcely necessary to go through the whole of the skeleton. I have brought 
to your notice the fact that bone begins to develope at this period of uterine life. 
I should have liked to have shown the new formed bone, but from various 
causes I have not been able to do so, For a long period after birth a thin layer 
of unossified cartilage remains between the extreme articular end of long bones 
and their shafts, until their growth is fully completed, their function taking 
place either at the period of puberty or towards the end of the period of growth. 
It is important that surgeons should know when the epiphysis become joined to 
the shaft, as it aids in diagnosing many injuries to which joints are subject, for 
it not unfrequently happens that on application of severe force to a joint, 
the epiphysis may be separated from the shaft, and such injury might be mis- 
taken for fracture. 
GROWTH OF BoNnE.—Increase in length, by development of new bone in 
the cartilage at either end, and in thickening by the deposition of soft ossifying 
blastema in successive layers upon the inner surface of the periosteum. 
There are 200 distinct bones in the human skeleton : 
Vertebral Column, including | 
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Oa caliyMid es, x js Gemma gam Cs ER NOS a2 9 J cenctck up-c dice't sw aici eeamucakiict ee 26 
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200 
There are sometimes a few very small loose bones called the Wonnian bones 
found in the sutures between the bones of the head. The bones of the ear are 
three, and occasionally some seed-shaped bones are found. The teeth are not 
included. There are twelve ribs on each side of the body; the first seven are 
connected with the sternum or breast bone by cartilages, this allows the chest 
walls to enlarge when we inhale the air, they rising up to increase the size of 
the chest. The first seven ribs, called sternal or true. The remaining five are 
asternal, or false ribs, and the last two, shorter than the rest, floating ribs. 
The ribs articulate with the spinal column and the sterum. 

Nore. Thereis an opinion, I believe I might say a popular one, that in amputating a 
limb the greatest pain is felt when the marrow is cut through. This, I need scarcely 
say, is an error. 
Norte. Shaft, Diaphysis. Ends, Epiphysis. 
