GERDY ON THE INTIMATE STRUCTURE OF BONE. 29 



recent bone, indicate the position of these vessels. Having 

 entered the compact tissue, they spread in its channels (canals 

 of Havers, canaliculi of Gerdy^) which are imperceptible 

 without a microscope in a healthy bone, but beconae, very 

 manifest in disease. 



Those of the medullary canal enter usually by a single large 

 foramen, give off some branches to the canaliculi in their course, 

 and having reached the medullary or central cavity, divide into 

 two branches, which run in opposite directions towards the 

 extremities of the bone. These branches divide and subdivide 

 very minutely in the medullary membrane, and anastomose 

 very freely with the vessels of the canaliculated tissue upon 

 the side, and in the adult, (after the cartilage which separates 

 the epiphysis from the body of the bone has been removed,) 

 with the cellular tissue of the extremities. 



Those of the cellular tissue, that is to say the vessels of the 

 extremities of the long bones and the large vessels of the other 

 bones, penetrate from the surface by foramina much larger than 

 those of the compact bone, and occasionally under the form of 

 distinct canals. They are very numerous. I have counted 145 

 on the lower end of the femor, 25 upon a vertebra, and. 30 on the 

 os calsis. They anastomose intimately with the other two orders 

 of vessels, and are particularly abundant near the articular sur- 

 face of the bones, where they form the tubular cells, and as some 

 suppose, directly or indirectly assist in the formation of the 

 articular cartilages, which many have considered a simple pro- 

 duct of excretion like the nails or hair. All the vessels are sur- 

 rounded in the canals by a cellular tissue, more or less delicate 

 loose and filled up with a fatty or oily matter, which is least 

 abundant in the compact tissue where the canals are very small. 

 No other nerves except those which accompany these vessels 

 are believed to enter the substance of bone. These facts in 

 regard to the structure of bone are supported both by observa- 

 tion and reasoning. The microscope shows us thousands of 

 vessels in the healthy state entering into the substance of the 

 bones. Inflammation attended with vascular congestion develops 

 and renders them so obvious as to be appreciated by the 

 3* 



