0)1 Certain Parasites of the Mouth in Cases of Pyorrhoia. 517 



of a hard toothbrush ; this mi_ifht account for the fact, pointed out 

 to us by Mr. Buxton Eyle, of Oxford, that this kind of recession is 

 liable to be more advanced on the left side of the mouth of a 

 right-lianded person, and vice versa. Of course there are many 

 other ways of accidentally injuring the gums which will readily 

 occur to all. N^ow, we should like to suggest that if after injury 

 to the gum the teeth are not kept free from tartar and otherwise 

 clean, the inflammation will increase and spread until a general 

 gingivitis is caused, and that this, if not checked, will be followed 

 by the appearance of all other symptoms of pyorrhoea. 



This is, of course, merely a suggestion, and the only evidence 

 in its support that we can give is the very common occurrence of 

 general gingivitis and pyorrhoea among soldiers returning from 

 active service. They nearly all say that it was practically impossible 

 to keep their teeth clean while in the trenches, and the condition 

 of their gums certainly improves rapidly after the removal of the 

 tartar by a skilful dentist and the frequent use of antiseptic mouth- 

 washes, etc. 



There is one more point to be noted among general appearances, 

 and that is the frequent occurrence of brownish, slightly refringent 

 granules of irregular shape deposited just below the epithelium, 

 apparently brought there by capillaries. By reflected light this 

 su bstance appears black, and was first noticed on the flaps of gum 

 left attached to extracted teeth, which are sometimes distinctly 

 speckled with black in consequence. 



It will be well before proceeding further to give a brief account 

 of the positions in which the tartar or calculus is found. As will 

 be explained below, this is of organic origin, the formative organism 

 Leptothrix belonging to the higher bacteria or lower plants. When 

 its growth is not interfered with it generally forms a ridge just at 

 the margin of the gum. After calcification to form " hard " tartar 

 this is very firmly attached, but in its earlier stages, when with other 

 bodies from the mouth it forms the soft tartar (or " materia alba " 

 of Leuwenhoek, 1683), it may easily be removed. In an extracted 

 tooth (fig. 5) the ridge of hard tartar is just at the top of the gum- 

 flap which generally comes away with it, since the gum breaks at 

 its weakest spot, viz. the lesion opposite the tartar ridge. As the 

 gum recedes the tartar follows it, and on very neglected teeth 

 forms a continuous encrustation, but on those that are even 

 occasionally cleaned the upper layers are removed to a greater or 

 less extent, so that a ridge may generally be distinguished (fig. 6). 

 The extent to which the ridge dips down on an extracted tooth 

 shows the depth to winch the pyorrhoea pocket had extended ; for 

 example, there is clear evidence of a deep pocket having existed 

 down one root of the tooth in fig. 6. Sometimes a pocket will 

 extend under the crown, and here also will be found a deposit of 

 tartar. At other times a whole root may be found to be involved. 



