OP THE BONES. 381 



bly so in slow and insensible growth, but the rapid elonga- 

 tion which takes place before the epiphyses become united, 

 evidently depends upon an addition of bony substance to the 

 end of the body of the bone, as is proved by the following 

 experiment of Hunter's. The tibia is. laid bare in a young 

 hog, and perforated at the two extremities of the ossified body, 

 the interval between the two holes being carefully measured. 

 Some months after, when the growth has advanced, the same 

 distance is found to exist between the two bones, and all the 

 elongation that has taken place has been beyond the hole, at 

 the extremities of the diaphysis. 



These experiments, which leave little to be desired with 

 respect to the growth of the bones, do not by any means afford 

 results so satisfactory respecting the habitual nutrition of the 

 bones. To redden the bones of a young animal, it is sufficient 

 to give it a few drams of madder, during a period of some 

 days, while the same substance given in greater quantity, and 

 during weeks or months, to an adult animal, hardly imparts 

 any colouring to them. 



603. After the growth in extent has ceased, the bones still 

 undergo farther changes, the most remarkable of which is their 

 decrease.* The medullary canal of the long bones continues 

 to increase in diameter from the moment of their formation. 

 So long as the growth in thickness continues, the walls of the 

 canal being augmented at the exterior, preserve their thick- 

 ness, and even increase in that direction. 



Duhamel made a very curious experiment on this subject, 

 although he drew false inferences from it. Having laid bare 

 and surrounded with a metallic wire a long bone of a young 

 animal which he killed some time after, he then found the 

 wire covered over by the bone which had increased in thick- 

 ness, and the canal, having acquired the diameter of the metal- 

 lic ring, he concluded from this circumstance that the bone 

 had enlarged by expansion, by the widening of its canal. This 

 is not the case, however. The bone had increased at its ex- 



* Albinus. JLnnot. Acad. F. Chaussard. Hccherchcs sur I 1 'organ, des vicil- 

 lards. Paris, 1822. 



