1885.] 



On Trichophyton tonsurans. 



415 



Taking into account the superior thickness of the basalts in Mull, and 

 above all the presence of ash beds atf their base, it seems probable that 

 they were nearer the vents than Antrim, and that their lowest beds 

 are at least not newer, so that the Mull leaf-beds at 150 feet from 

 the base should be much older than the Glenarm and Ballypaladv 

 leaf-beds at 600 feet from the base. 



The horizontal extent of the fluviatile beds of Mull is more difficu't 

 to estimate. Gravel is mentioned as present at Loch Truadh, to the 

 north-west, and at Carsaig to the east. In the latter locality it is, 

 perhaps, thicker and more extensive than at Ardtun. The horizon 

 should also be found in two of the Treshnish isles and round the 

 north-west coast of Mull, and there can be little doubt but that 

 deposits of plants exist in many localities besides Ardtun. Black 

 shales, with identical leaves, have been found in Canna, and leaflets 

 of Taxus or a similar foliaged conifer at Uig. 



Though the fluviatile beds at Bourg are unfossiliferous, a very 

 interesting relic of the Eocene vegetation occurs there, for a large 

 tree, with a trunk 5 feet in diameter, has been enveloped as it stood 

 to a height of 40 feet, by one of the underlying lava beds. Its solidity 

 and girth enabled it to resist the fire, but it subsequently decayed, 

 leaving a hollow cylinder filled in with debris and lined apparently 

 with the charred wood. There is also the limb of a larger tree in a 

 fissure not far off. The wood proves to be coniferous, belonging 

 possibly to the Podocarpus whose leaves are so conspicuous in the 

 beds above. 



III. "Addition to a former Paper on Trichophyton tonsurans" 

 (« Proc. Roy. Soc," vol. 33, p. 234.) By George Thin, M.D. 

 Communicated by Prof. M. Foster, Sec. R.S. Received 

 December 3, 1885. 



In the " Proc. Roy. Soc," vol. 33, p. 234, 1881, a paper of mine is 

 published on " Trichophyton tonsurans*' 



Since the time that the investigations recorded in that paper were 

 made, the study of parasitic fungi has been greatly facilitated by the 

 introduction by Dr. Koch of gelatinised meat juice as a medium for 

 cultivation, and having again studied the development of tricho- 

 phyton with the advantages derived from the use of this medium, I 

 believe that two results which I have obtained might be usefully 

 published as a supplement to the paper referred to. 



The gelatinised meat juice which I used was peptonised and 

 neutralised, and trichophyton grew on it readily and with certainty. 



In my previous experiments (in which I used vitreous humour) I 

 had succeeded in growing the fungus when the hairs containing the 



