"He found that the capsule surrounding each ball of capillaries (the glomerulus) in the nephrons (the blood filtration units of the kidney) is a continuous part of the renal duct, which eventually drains urine into the bladder. This structure, now called Bowman’s capsule, was of prime importance to his filtration theory of urine formation, which is the most important element in the present understanding of kidney function. Bowman and Todd’s investigations resulted in their The Physiological Anatomy and Physiology of Man, 2 vol. (1845–56), a pioneering work in both physiology and histology."

works on the structure of striated muscle

"important piece of work [on] the structure of the muscous membrane of the alimentary canal"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC513067/?page=6

 

“ The Manuscripts of Sir William Bowman was given on 18 June 1840; until the recent advent of the electron microscope histologists have been able to add little to Bowman's original description of striated muscle of 125 years ago.”

 

“Bowman's original contributions to the surgery and medicine of the eye were many. Histologically he described the cornea, including its anterior elastic membrane, Bowman's membrane: the radial fibres of the ciliary muscle.” Page 248-250 The Manuscripts of Sir William Bowman by K Bryan Thomas

 

“he graduated to London, as demonstrator in anatomy, at King's College, taking advantage of a new microscope (the reward for his exact calibration of the cardiac orifices) to unravel the intricacies of human histology.These had to be gleaned from teased-out tissues, as seen by reflected light, since stained sections were not yet available.” British Journal of Ophthalmology,1992 volume 76

 

“The three most important subjects of Bowman’s researches were (1) the structure of muscular fibre, (2) the structure of the kidney, and (3) that of the mucous membrane of the alimentary canal.” Nature, April 14^th 1892