While seeking a method to determine the capillary blood pressure, Lombard1 discovered that the circulation in the capillaries of the living person could be observed with a microscope. The skin was rendered transparent with either glycerin or cedar oil. Magnifications of from ten to twenty-five times were found best. For illumination he used either a Nernst lamp or daylight. Later Weiss2 observed the capillaries of persons suffering from various diseases. In his method the electric light rays pass through a series of lenses before striking the area of skin to be illuminated; later, he used only one lense.3 In determining capillary blood pressure, Danzer and Hooker4 used merely a strong electric light and castor oil with their pressure apparatus and objective 3 and ocular 4 of the microscope.
The apparatus used to make my observations is very simple and not bulky. It consists of a small