70 BRITISH BIRDS. 



as occurring during acorn or beech-mast years, though 

 the causa morhi has not been so generally understood. 



In British Birds (Vol. I., p. 243) I gave an account 

 of the micro-organism which was responsible for the 

 disease, the naked-eye appearance of birds dead of the 

 disease, and other facts as far as were known. In order 

 to ascertain more facts concerning this matter, at the 

 suggestion of the Editors of British Birds, I drew up 

 a schedule of questions which was sent round to all 

 readers of the Magazine for the purpose of securing help 

 from those who were interested in the subject, and the 

 results of this enquiry I now set forth. I must here 

 express my great indebtedness to all those who filled 

 in schedules, and so kindly supplied the information 

 upon which the following conclusions and suggestions 

 are based. 



I have thought it better to group the facts under the 

 following headings : — 



I. — Geographical distribution. 

 II. — Migratory flocks. 

 III. — Transmission of the disease. 

 IV. — Duration and course of the disease. 

 V. — Relation to food supply. 

 VI. — Transmission to other animals. 

 VII. — Post-mortem appearances. 



I. — Geographical Distribution. — From the ac- 

 companying map it will be clear that the reports show 

 that the disease was almost entirely confined to those 

 counties which border the Thames Valley. The only 

 positive returns received from other more distant 

 counties were from Yorkshire, Cumberland, Norfolk, 

 Essex, and doubtfully from Devon. Now, from all 

 these counties the reports seem to show that the 

 disease was local, or confined to isolated birds. For 

 instance, in Norfolk no disease was noted until the first 

 fortnight in February, when only one or two birds with 

 disease are recorded, whilst there is definite evidence 

 that the only occurrences in Essex were those from a 



