Curationum medicinalium centuria prima, multiplici variaque rerum cognitione referta. Praexfixa est eiusdem auctoris commentatio, in qua docetur, quomodo se medicus habere debeat in introitu ad aegrotantem, simulque de crisi, & diebus decretoriis, in qui artem medicam exercent, & quotidie pro salute aegrotorum in collegium descendunt longe utilissima.

Lusitano has been credited with early recognition of the circulation of the blood. How much he might have understood the circulation remains in doubt; however, through dissections of the Azygos vein, he was the first to observe and record his observations of the venous valves.
In Centuria I, paragraph (Curatio) 513 Lusitano described how, in 1547, he performed an experiment before some scholars from the University of Ferrara, blowing air into the lower part of the azygos, and showing that the vena cava would not be inflated. It was not possible for the air to escape because of the valve or operculum mentioned. The anatomist Giambattista Canano, witnessed these experiments, and discovery of the valves was later attributed to him by mistake.

Of 16th century Jewish physicians, Lusitano may have been the most significant in terms of the number of his scientific contributions and the extent of his publications.

Digital facsimile from Google Books at this link.