On Trichophyton tonsurans (the Fungus of Ringworm). 241 



In a large proportion of them, however, freshly extracted hairs were 

 used. 



2. Cultivation in cells at room temperature. No growth took 

 place. 



No. of celis. No. of days. 



1 2 



1 10 



3. About the time when the experiments referred to in the above 

 tables were ended, it occurred to me that the reason why the spores 

 did hot grow was because the hairs were submerged in the fluid. 



Acting on this idea, I moistened the under side of the cover-glass 

 of the cell, taking care that the roots of the hairs used were not 

 covered with the fluid. For the first time I obtained evidences of 

 undoubted growth. The convenience of the cell for such experiments 

 was now well shown, as I was able to observe the earliest evidence of 

 mycelial growth from the spores on the sides of the hairs without 

 disturbing the preparation, which could be put back again into the 

 incubator without any part of it being moved. In these instances 

 there was no possibility of a mistake being made by confounding adven- 

 titious fungi with trichophyton. The spores of the latter could be 

 examined in situ through the cover- glass, and as germination took 

 place the spores could be seen elongating into a mycelium from their 

 original position on the edge of the hair. 



In three cells prepared in this way trichophyton grew. The 

 first appearance of elongation in the spores was observed after the 

 preparation had been a few hours in the incubator, the hairs having 

 been transferred from the head of the child to the incubator after a 

 very short interval. During the two following days the growth went 

 on to the formation of mycelium. The mycelium, however, ceased to 

 grow after having attained a very moderate length ; spore formation 

 soon beginning to take place. 



(Similar cells prepared in the same way with Cohn's fluid and with 

 hairs from the same patch showed no signs of growth.) 



The disadvantages associated with this mode of cultivation were 

 found to be the following : — 



It was difficult to hit on the right quantity of fluid. If there was 

 too much the spores did not grow, and if there was too little 

 they did not grow, and when the quantity happened to be sufficient 

 to encourage germination it was not enough to maintain growth after 

 the mycelium had attained a comparatively limited length. 



This difficulty was got over in the following way : — 



4. When the hair was laid gently on the surface of vitreous humour 

 in a test-glass, it did not sink, and by simply floating the hairs I was 

 able to secure the requisite conditions of moisture without immer- 

 sion. 



