72 THE MICROSCOPE. 



FROM CARTILAGE TO BONE AS SEEN BY THE MICRO- 

 SCOPE. 



BY JOHN H. LOBDELl, M. D., 

 Pro/eisor of Histology Michigan College of Medicine. 



THE change from cartilage to bone is a process which is under- 

 stood, and, I may say studied, by but very few physicians and 

 surgeons of this country. 



It is a process of much importance, as it begins in the embryo 

 and ends only when death ends every function of the body. There 

 was no close study of the change until within the present century, 

 and then owing to the poor facilities the study was incomplete and 

 some of the most important conclusions erroneous. 



It is only within a few years that the correct conclusions have 

 been arrived at. For many years those studying developing bone, 

 owing to their poor facilities, supposed that cartilage cells became 

 directly transformed into bone cells ; but this is not the case. I 

 will, I think, safely say that the cartilage cell directly has nothing to 

 do with the formation of the bone cell. The bone cell is an inde- 

 pendent formation owing, as I have said, nothing to the cartilage 

 cell. I will make my paper of as few words as possible covering 

 the subject. 



The first step of the change is the development of small capil- 

 laries and blood-vessels within the substance of the cartilage. Now 

 begins the breaking down of the cartilage substance and cells. 

 Owing to the metamorphosis of the melting cells we have formed 

 blood globules, fat cells, marrow cells, connective tissue cells, pus 

 cells, etc. The points of developement of the blood-vessels appear 

 as small round reddish masses, but under the microscope these 

 masses are found to be the blood-vessels filled with reddish brown 

 cells destined to take an active part in the formation of bone sub- 

 stance. By careful observation with high power, small cavities are 

 found within the ruptured cartilage capsules lined with small cells re- 

 sembling epithelium, 'ihese are, or are to become, the so-called 

 osteoblasts. It is from these osteoblasts that the deposition of the 

 basis substance of the bone tissue takes place, in an outward di- 

 rection. 



By more careful examination cells of the osteoblast may be seen 

 pushing their way in the cartilage substance to become centers of 



