1)U. HEALK, OX THE Tl.SSUESJ. 17 



germinal matter, whieli they contained, liaving imdergoue 

 conversion into formed material, they ceased to be coloured 

 by carmine. They now look like roundish, highly refracting 

 cords, ■which are colourless, and connect the several stellate 

 masses of dark-red germinal matter with each other. Here 

 and there in the intervals between these processes small glo- 

 bules of calcareous matter have been deposited, and these in- 

 crease and completely surround the cord-like processes. 

 Many of the processes gradually assume the character of 

 the surrounding matrix, disappear as distinct cords, and like 

 the rest of the tissue become impregnated with calcareous 

 matter. 



Many of the stellate masses of germinal matter (cells) 

 shrink and disappear in consequence of the same changes 

 having occurred. Others remain with their processes, and 

 their nuclei possibly remain as the nuclei of the lacunae which 

 are irregularly distributed through the cementum ; but Dr. 

 Beale could not express himself positively on this point. It 

 is certain that all the cells do not become lacuna, for in this 

 tissue there are half-a-dozen stellate cells to one lacuna in 

 the cementum, and many of the canaliculi are five times as 

 long as these tubes. Arc these processes tubes ? This ques- 

 tion would doubtless be answered in the affirmative by every 

 one who examined the tissue long after death, but daring life 

 they contain a solid, or semi-solid, substance corresponding 

 to that Avhich occupies the so-called dentinal tubes. They 

 contain portions of the germinal matter which is undergoing 

 conversion into formed material, and the situations in which 

 these tubes existed arc the last portions of the formed mate- 

 rial to undergo calcification. 



This is precisely the same change Avhich takes place in the 

 calcification of the dentine, the only diffei*ence being in the 

 forms which the masses of germinal matter assume in the 

 first instance. It need hardly be remarked, that cementum, 

 as it ordinarily exists upon the fangs of the human teeth, 

 differs from true bone in its greater degree of hardness, in 

 the small mmiber and irregular arrangement of its lacuna, 

 and in the absence of the arrangement for its absorption 

 and reproduction. It is a more permanent but less perfect 

 tissue than bone. 



Stellate fibre cells from the aorta. — Attention was next 

 drawn to a very thin section of the circular coat of the aorta, 

 coloured by soaking in carmine, showing large stellate 

 muscular fibre cells. It Avill be interesting to compare this 

 with the tissue upon the fang of the tooth. The radiating 

 processes seen in this specimen are clearly not tubular ; the 



VOL. II. NEW SER. B 



