This paper deals with the merging of science and medical practices in the 1930s, in the context of the attempts to legitimate biotypology as a foundational medical doctrine for clinical medicine (especially propaedeutic clinics) in Brazil. The aim is to examine how Brazilian physicians mobilized scientific arguments and practices of bodily quantification and statistics to give scientific status to their clinical practices. The most common definition of biotypology is “the science of constitutions, temperaments and characters”. However, the term has additional meanings which can be found in the discourses of contemporary physicians. Biotypology also represented ‘the scientific stage of constitutionalist doctrine’ and was viewed as the transition of the constitutional doctrines from empiricism to science. It was also characterized as “the science of human individuality”, “the science of personality”, “the science of individual difference” and “the science of the architecture and engineering of the individual human body”. It is notable that in all these definitions, biotypology was often followed by the word “science”, with the aim of bringing a new and more scientific outlook to traditional constitutional medicine. At the same time, constitutional medicine, through biotypology, was proposed as a way to overcome the reductionist approaches of some laboratory practices which focused mainly on illness and not on individuals. In this outlook, the individual was a promiscuous object in which science and clinics could meet. The main scientific practices of biotypology consisted of morphological, physiological and, sometimes, psychological measurements, connected with mathematical equations and statistics. Moreover, it used several scientific instruments for body quantification originated in anthropometry (e.g. compass and goniometer), and physiology (e.g. spirometer). All these procedures and theoretical grounds were combined to produce a bodily classification of Brazilians – biotypology was also a “comparative biology of human beings” –, to establish patterns of normality, and to characterize the individual in biological terms. In this paper, I argue that through the entanglement of experimental practices and statistics with the constitutionalist study, i.e. the look at the individual, Brazilian physicians attempted to incorporate a “bio” compound in their ways of knowing and clinical practices.