514 Transactions of the Society. 



sections are from dogs or cats ; in these animals the disease runs 

 much the same course as in man. 



The normal tooth (figs. 1 and 2) has its roots deeply em- 

 bedded in its socket in the bone of the jaw, and is separated from 

 the bone by a layer of fibrous connective tissue, the peridental 

 membrane, and is firmly held in position by a strong ligament. This 

 ligament is attached normally to the very top of the crusta petrosa 

 at the place where this layer of bone joins the enamel of the crown. 

 The epithelium of the gum dips down round the tooth and reaches 

 the ligament. Normally the gum lies closely apposed to the tooth, 

 practically obliterating the so-called gingival space (figs. 1-3). 



Even in healthy gums leucocytes from the lymph glands may 

 be seen making their way through the epithelium, and we maintain 

 that these glands are the main source of the salivary corpuscles 

 always found in the mouth, and not the tonsils as stated in 

 text-books. The corpuscles which make their way through the 

 epithelium opposed to the tooth collect in the gingival space 

 ("espace pericervical "), where Mendel {10)* has recently recorded 

 their presence in healthy persons. We have also found them in 

 the very long gingival spaces round the incisors of rabbits with 

 healthy gums. 



We may now pass on to the pathological changes effected by 

 pyorrhoea. Probably the very distressing symptoms are well known 

 to you. The clmical aspects of the disease have been much dis- 

 cussed and the most diverse opinions and treatments put forward, 

 often without much scientific basis. It is from the strictly 

 scientific side that we wish to attack the problem, and the obser- 

 vations given here — the result of a year's study of many hundreds 

 of cases — are merely by way of a preliminary communication. 



The symptoms in advanced cases may be summed up as — 



1. Acute inflammation of the gums, accompanied by the 

 collection of pus and a large deposit of tartar round the teeth. 



2. Absorption of the edge of the socket (alveolus) and reces- 

 sion of the gums so that a large portion of the tooth projects, and 

 it later becomes loose and falls out. 



From a study of mild cases it is quite clear that the lesion 

 starts near the summit of the gum (fig. 4), not at the bottom of 

 the gingival space, as the diagrams and description given by Bass 

 and Johns {1, pp. 55, etc.) seem to imply. This space remains 

 for a time lemarkably free from organisms. The place where the 

 inflammation starts is directly in contact with any tartar present 

 (fig. 5). Unfortunately, during decalcification of teeth for histo- 

 logical purposes, the tartar ridge nearly always becomes detached; 

 in the tooth shown in fig. 7, however, and on the lingual side of that 

 shown in fig. 8, it remains more or less in position. The large 



* The numbers within brackets refer to the Bibliography at end of the paper. 



