He accomplished this by using the ear canal's ear drum's blood vessels, which are shared with the hypothalamus. Before the ear thermometer's invention, easy temperature readings could only be taken from the mouth, rectum, or underarm.
The passage describes a method for measuring body temperature that utilizes the ear canal's eardrum's blood vessels, which are connected to the hypothalamus. This method was an alternative to traditional methods of taking body temperature like the mouth, rectum, or armpit.