472 



LECTURE XIX. 



which I have rarely had occasion to witness, the transi- 

 tions from periosteal connective tissue into osteoid tis- 

 sue, and this too with a peculiar modification, inasmuch 

 as calcification has not taken place in large portions of 

 the parts which already possess a structure of bone. The 

 preparation comes from a tumour in the jaw of a goat, 

 and contributes towards our knowledge of the transi- 

 tions from connective tissue into osteoid tissue about 

 the same information, that the history of rickets has 

 supplied us with concerning the transformation of carti- 

 lage. The tumour which affected the superior and infe- 

 rior maxillge, but each separately, has such little density, 

 that it can be cut with great facility, and only in a few 

 places does the knife meet with greater resistance. On 

 making thin sections, we see, even with the naked eye, 

 that the more and less dense portions alternate with 

 each other, so that the whole has a reticular appearance. 

 When examined under the microscope with a low power, 



FIG. 131. 



Fig. 131. Section from the sofc osteoma from the jaw of a goat showing the 

 characters of periosteal ossification. Networks of osteoid trabeculse with jagged 

 cells enclose primary medullary spaces, filled with fibrous connective tissue. The 

 dark parts represent calcified and completely developed osseous tissue. 150 dia- 

 meters. 



