524 Transactions of the Society. 



branches of a peculiar type, as shown in our illustrations (hg? 

 16, 21). To these we have given the name of "bottle-brushes." 

 They consist of a few central threads with innumerable fusiform 

 bodies, which are usually slightly curved, so set upon this stem 

 as to make it resemble a little fir-brancli. Sometimes these 

 fusiform bodies appear to be firmly attached to the branch, but in 

 other specimens they may be watched coming off the axial threads 

 in clouds, and in this condition they appear to be motile. They 

 have often already divided into a diplobacillary form, while still 

 attached to the stem. Branches are frequently found which have 

 already shed these bodies from their distal portions, but aj'e still 

 closely beset with them lower down. In this condition the distal 

 portion of the branch is seen to be covered with little coccoid bodies 

 which at a later stage appear to have budded off more coccus 

 forms in the typical radiating rows, while the lower portion may 

 still be covered with fusiform bodies. This fusiform bacillus 

 appears to be the one associated with a spiroclmet in A^incent's, 

 angina.* With regard to the " iodine reaction " recommended by 

 so many authors for differentiating the different species of bacteria 

 found in the mouth, we have made the following? observations: — 

 The radiating bundles of coarse threads usually give this purple- 

 red reaction ; the intensity, however, varies very much, from nearly 

 black to a hardly discernible tint. If long coarse threads project 

 singly far beyond the surface of the colony they almost invariably 

 do not give the reaction. Some of the finer threads in lobose 

 branches of a colony usually give it, but as a rule it is only a few 

 at intervals that do so. Sometimes a whole colony fails to give the 

 reaction. Occasionally whole branches stain deeply with iodine — 

 central threads, shorter radiating threads, coccus-form, and all. In 

 a cat we have even found bottle-brushes with the attached fusiform 

 bacilli staining right through. Often a few areas of the coccus-form 

 in a colony give the reaction. It seems to us that the iodine re- 

 action may be regarded as merely showing the presence of a food 

 substance which may be stored in different parts of a colony, 



* On a few occasions it more resembles the Bacillus necrosis (see Eller- 

 mann (4)), that is to say, it is longer, and has a striated appearance due to the 

 distribution of the granular contents. 



EXPLANATION OF PLATE XVI. 



Fig. 17. — Young colony of Leptothrix from the tongue, growing on a core of dead 

 epithelial cells, which are already partly calcified. Drawn from a fresh 

 preparation stained with iodine. The coarse threads leading to little 

 branches gave the iodine reaction, x 300. 

 ,, 18. — Two coarse threads of Leptothrix, stained with iodine, showing the 

 granules giving the purple reaction in the segments.' x 3500. 



[ „ 19. — A group of partly calcified clubs, from the periphery of a Leptothrix 

 colony. X 625. 



