Superior nutrients are taken in via bloodstream to heart and dispersed to cells via general bloodstream. Normal digestion converts into mucus, saliva, and gastric and intestinal mucus. Abnormal digestion causes excess mucus, classified as sweet, sour, thick, thin, etc. Normal bile is formed in liver, affects blood, and acts in small intestine. Abnormal humor causes destructive changes in bile.
Normal humor affects spleen and blood, and mixes with phlegm humor.
Fourth digestion Abnormal humor is passed out as ash or admixes with blood humor and other humors, producing morbid conditions. The invention of the microscope has taken us away from the source and origin of the problems associated with disease. For example, most physicians would attribute an infection to one or more bacteria and will produce actual living specimens of those bacteria which they say caused such and such an infection. From the Unani Unani point of view, the deviation from the normal state of the humor provided a suitable environment for the bacteria to grow to larger than normal populations. While admitting the existence of the bacteria, the Unani scientist must look deeper to the cause of the imbalance in the humor and its characteristic temperaments.