Ann Arbor Scientific Association. 15 



trophy. He referred to the fact that most histologists figure the 

 cement as containing bone-corpuscles ; and then stated that, 

 from frequent and repeated observation ot various specimens, he 

 had concluded that true cement is nearly, if not entirely, desti- 

 tute of what are called bone-corpuscles, and that the so-called 

 bone-corpuscles found in cement are but the corpuscles which 

 were developed when the cement-organ was in a state favorable 

 to hypertrophy. 



In hypertrophic cement, it is true, these corpuscles are very 

 numerous, having broad, flattened bases, resting upon the exter- 

 nal surfaces of the lamina, with canaliculi extending towards the 

 periphery of the tooth. They vary much in size, and sometimes 

 several are joined together. He considered them simply masses 

 of periosteal tissue which have become enveloped within the 

 rapidly growing cement. 



There are occasional specimens when the hypertrophy is ho- 

 mogeneous. The corpuscles in such cases somewhat resemble bone- 

 corpuscles. In these cases there are also present distinct tubuli, 

 running parallel to each other with undulating or tortuous courses, 

 somewhat resembling the dental tubules, but larger. These are 

 not found in true cement. Again, that which is called the ce- 

 ment or bone-corpuscle is not necessary to the physiological 

 structure of true cement, and, when found, is the result of a 

 pathological condition of the part at the time of its formation ; 

 and, therefore, the presence of hypertrophic cement shows a 

 pathological condition of the part, although the disturbance may 

 not have been material. 



A discussion of the facts set forth was engaged in by Profs. 

 Prescott, Harrington, and Dr. Jackson. Prof. Harrington re- 

 marked that the shape of the corpuscles as described by Dr. 

 Jackson was much like many seen in the bones of the ox and 

 horse. He also said that many authors state that the bone-cor- 

 puscle is a hollow, hard structure which will be left behind after 



