In this country clinical examinations of the blood have hitherto been employed almost exclusively by the Physician, and generally in those conditions known as "Diseases of the Blood."
In American and Continental Hospitals haematological examinations have been adopted as a clinical method with a much wider application. We now know that such examinations can give information to the physician in diseases other than diseases of the blood, and further, that they can be of the greatest value to the surgeon. Quite three fourths of my observations upon this subject have been made upon surgical cases, and none of the medical cases I have examined were suffering from any of the so- called "Diseases of the Blood." It is the blood which sustains the vitality of every organ in the body. Through it the products of constructive and destructive metabolism are carried to their respective destinations, therefore it ought not to be surprising that a careful examination of its . several elements should prove of value to the clinici an. The necessary technique for such examinations has been improved very considerably during the last ten years, and a very satisfactory degree of accuracy can be claimed for our results at the present time. We owe a very great deal to men like Ehrlich, Thoma, Hayern, and many others, not only for their great scientific genius, their emphatic pathological conclusions and their brilliant histological results, but also for that scientific accuracy and,untiring perseverance which cannot fail to bear fruit in the younger generation of scientific workers.
A complete examination of the blood occupies so much time that it is almost impossible for the busy practitioner to carry it out with any degree of regularity.With this feeling in my mind, I have worked at the subject of leucocytosis in order to determine how much information is likely to be obtained by such a partial examination of the blood as simple quantitative estimation of the white blood corpuscles. Every medical practitioner accustomed to the use of the microscope, will have no difficulty in counting leucocytes, and it can be done in so short a time that it ought to be possible to the busiest of us.