Rembrandt "Danaë", 1636), seeking to emulate the baroque style of Rubens. With the occasional help of assistants in Uylenburgh's workshop, he painted numerous portrait commissions both small ("Jacob de Gheyn III") and large ("Portrait of the Shipbuilder Jan Rijcksen and his Wife", 1633, "Anatomy Lesson of Dr. Nicolaes Tulp", 1632). By the late 1630s Rembrandt had produced a few paintings and many etchings of landscapes. Often these landscapes highlighted natural drama, featuring uprooted trees and ominous skies ("Cottages before a Stormy Sky", c. 1641; "The Three Trees", 1643). From 1640 his work became less exuberant and more sober in tone, possibly
Nicolaes Tulp the condition we know as migraine, the devastating effects of tobacco smoking on the lungs, and reveals an understanding of human psychology in a description of the placebo effect. Tulp also discovered the ileocecal valve at the junction of the large and small intestines, still known as Tulp's valve. While Tulp made observations of various diseases, treatment often continued in the age-old way. His description of the symptoms of Beriberi in a Dutch seaman, for example, went unnoticed until the cause (vitamin B1 deficiency) was recognized two hundred years later by Christiaan Eijkman. Partially as a result of the success