LIFE HISTORY OF BACILLUS ANTHRACIS. 161 



any adventitia. The vessels larger than this possess an external 

 coat of connective tissue, and I am inclined to think that below 

 this there is only the layer of endothelial cells, which in these 

 larger vessels are modified so as to form incomplete hoop-like or 

 circularly-disposed elements. This appears to be the interpreta- 

 tion which must be put upon the silver-outlines drawn in fig. 8. 



I have not at present investigated the structure of the con- 

 tractile vessels, which should yield interesting results with 

 silver-staining, and also when prepared as transverse sections. 



The foregoing observations were made in the histological 

 laboratory of Exeter College, Oxford, being part of a more 

 extended investigation of the structure of the renal tubes or 

 nephridia of the Earthworm. 



On the Life History of Bacillus anthracis. By J. 

 CossAR EwART, M.B., University College, London. With 

 Plate XI. 



Through the kindness of Dr. Burdon Sanderson, Super- 

 intendent of the Brown Institution, t have been enabled to 

 repeat the well-known inquiries of Cohn and Koch^ into the 

 life-history of Bacillus anthracis. This organism has been 

 described as a motionless, rod-sbaped bacterium, which, 

 when kept at a temperature of 32° C., lengthens out into a 

 long, thread-like filament, in which numerous bright, oval 

 spores are formed. The spores, when set free by the disin- 

 tegration of the filament, develop into rods which, when 

 introduced into the subcutaneous tissue of an animal, 

 increase indefinitely by a process of transverse fission and 

 set up splenic fever. 



In repeating the experiments made by Koch and others I 

 have especially directed my attention to the phases through 

 which the rods and spores pass, and, along with Dr. Burdon 

 Sanderson, I have endeavoured to prove that the spores do 

 not, as stated by Pasteur, resist the influence of boiling and 

 of pressure. 



In carrying on this investigation I made use of a hot 

 chamber, but found of especial service the warm stage ^ 



^ ' Die Aetiologie der Milzbrand-Krankheit, begriindet auf die Entwick- 

 lungsgeschicbte des Bacillus anthracis." 'Beitrage der Biologie der 

 Pflanzen,' Zweiter Band, Zweiter Heft, 1876. 



- See figure of warm stage in Mr. Schafer's ' Practical Histology.' The 

 stage may be had from Mr. Casella, 147, Holborn Bars. 



