Answer:Capillaries
Explanation: Capillaries are tiny, thin walled vessels that form a network to take blood through the organs and other body tissues. The dense networks of capillaries present a large surface area, which allows materials to be exchanged between body cells and the blood rapidly.
The results clearly reveal that Imipramine is by far more effective than Lithium in preventing the recurrence of depression. 62.16% of the patients taking Lithium had a recurrence of depression which is more than twice that of patients who took Imipramine (28.95%).
The results also question the effectiveness of Lithium in general since the percentage of patients who had a recurrence of depression in the Placebo group (67.65%) is only slightly higher than that of the Lithium group (62.16%).