VI PREFACE TO THE EIGHTH EDITION. 



or disease-inducing to the higher animals, when they have 

 passed through the blood of the lower forms of life, such as 

 Ticks, and have been transmitted by these into the circulation 

 of the higher animals. This view to some extent supports that 

 of Buchner, who states that the ordinary Hay Bacillus — Bacillus 

 suhtilis — attains all the virulent properties of the Bacillus 

 anthracis after it has been cultivated in animal media, meat- 

 extract, blood, &c. 



Since this work has gone to press, the Author has received 

 further corroboration of the seemingly anomalous occurrence of 

 simple filaments as retrogressive stages in the development of an 

 organism, apparently dependent upon a change in the nutrient 

 medium, — a fact previously noticed in the course of his 

 " Louping-Ill " investigations, 1882, which has led to a consider- 

 able amount of controversy. 



These so-called " involution " stages, as exhibited by the 

 Bacillus typhosus, will be found described and illustrated in a 

 paper by Dr. Edward P. Carter in the Bulletin of the Johns 

 Hophins Hospital for June of this year. 



The thanks of the Author are specially due to his colleague 

 Dr. James Hunter, whose unwearied labours and whose acute 

 judgment and profound learning have contributed greatly to 

 the fulness and accuracy of many of the illustrations, in them- 

 selves unique, in the present work. 



W. W. 



New Veterinary College, 



Edinburgh, September 1897. 



