PLATE 37. 



Photography of Culture Tubes. 



1. CULTURE OF Bacillus pi'odigiosus. 



2. CULTURE OF Sarcina. 



Direct colour photograph. Screen-plate process (Autochrome). 



Objective Goerz "Dagor" Anastigmat, 7" ', by Ross. 



Illuminant ... Arc, diffused light. 



Plate Autochrome. 



Screen Lumiere's special screen for arc-light. 



Exposure 15 sees. 



The production of the pigments is typical of the growth of these 

 organisms on various solid media. The B. prodigiosus causes the red 

 spots on bread giving rise to the appearance known as "bleeding 

 bread. " 



This photograph is reproduced with the object of showing the 

 device employed to prevent reflections on culture tubes, &c. The 

 tubes are immersed in water in a flat-sided trough, whereby the 

 reflections, visible on the top half of the tubes, are obviated. 



Photo. H. L. H. [To follow page 246. 



