The outbreak which is the subject of the present paper was discovered in the course of an enquiry which is at present being made on the request of the Home Secretary by Mr J. S. Martin, Inspector of Mines, and one of us, into the ventilation of Cornish mines. A number of cases of anaemia had occurred among the miners employed at Dolcoath Mine, Cornwall; and as the anaemia was generally attributed to some defect in the ventilation, this mine, was among the first visited. On examination into the state of the mine, the symptoms of the affected men, and the history of the outbreak, it appeared that the anaemia was almost certainly caused by ankylostomiasis. A more detailed enquiry, in which we have both been engaged, established beyond all doubt the nature of the disease, and has furnished the opportunity of investigating a number of points bearing on the nature and method of spread of ankylostomiasis. A short report on the outbreak has already appeared. We are indebted to Dr S. G. Scott, who has also been engaged in the Home Office Enquiry, for a number of valuable notes as to blood-examinations, and many other details.