PROCEEDINGS OF THE SOCIETY. 617 



A paper by Dr. Helen Pixell Goodrich and Miss M. Moseley, 

 entitled " Certain Parasites of the Mouth in Cases of Pyorrhoea," was 

 then read, Dr. Goodrich demonstrating, by means of a series of lantern 

 slides, the results of the authors' investigations. 



Sir E. Ray Lankester, K C.B., F.R.S., said it had given him great 

 pleasure to listen to this communication ; he knew that the authoresses 

 were engaged upon this work, and he was aware of some of their 

 investigations and found them of very great interest. The question of 

 the cause of pyorrhoea was one of much importance. The idea that 

 amoebge were responsible was prevalent when these ladies took up their 

 work, but he thought their view that the cause did not lie here would 

 be generally accepted. The study of the leptothrix they had described 

 was extremely interesting : it required careful and considerate treatment, 

 since it was a well-grown organism, and had a good deal of character 

 about it. 



The whole history of freely growing bacteria was one of great 

 interest, and had a close bearing upon medical pathology. Of course, 

 this creature in the mouth was very much like some of the organisms 

 concerned with calcifying springs, those hot-water springs which were 

 found in this and other countries, where they produced a deposit of 

 much calcareous matter. There had always been two opposed attitudes 

 in regard to bacteria— the one regarded every small form of bacteria 

 which could be isolated and made to exist by itself for a time, as a 

 distinct species or even a distinct genus. The other, in which he 

 included himself, considered that under slightly different conditions of 

 nutriment, bacteria might undergo very great changes in mode of 

 growth, and even in mode of movement and general shape. This was 

 what was called, at the commencement of the investigation, the 

 pleomorphic view, the view which he was pleased to find the authoresses 

 of this paper took in regard to the buccal organism they described. 



A point of great interest in this matter was that in dealing with 

 these more free-living bacteria, one was led rapidly through the 

 begiatoas and leptothrix and other such genera to a group of organisms 

 known to microscopists — namely, ostoria— to which group several genera 

 belonged. His belief, though he did not think many medical bacterio- 

 logists shared it, and some perhaps opposed it, was that the ostoria were 

 peculiar in their feeding, peculiar in their chemistry, and were alto- 

 gether a peculiar group of green algje. Many of the ostoria contained 

 chlorophyll, as well as other colouring matter. The bacteria were only 

 a specialized group, which had gone further. They exhibited the long 

 filamentous forms, but also exhibited coccus forms and short bacillary 

 forms ; their nutrition had become limited by the conditions in which 

 they lived. They had lived in rich fluids containing large amounts of 

 mineral matter ; and, living in special conditions of that kind, bacteria 

 had made their way from the outside of organic bodies to the inside, 

 losing their colour, and then losing much of their variety of growth. 

 Those were points of interest connected with leptothrix and the similar 

 bodies which were found in natural fresh waters. He was extremely 

 glad that these gifted ladies had taken up the subject, and hoped they 

 would carry it on, and in doing so have in mind not only the desira- 



Dec. 20th, 1916 2 u 



