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Gall, Flourens, and the Question of Cerebellar Function and Localization in Early Science
Nariah Fagan
PHILOSOP 2050: The Scientific Search for the Mind
Dr. Sullivan
Dec 9, 2025
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Historically, scientific attempts to understand the relationship between brain structure and
function have always posed the question: Are psychological functions able to be localized in
identifiable regions within the brain? This question was particularly prevalent during the
nineteenth century where physiologists attempted to map mental faculties to specific neural
structures. The tools available to early researchers, and the contrasts between observational and
experimental methods, reveal both the progress and limitations of early neuroscience. The debate
between Franz Joseph Gall and Pierre Fluorens is especially revealing as they both have different
perspectives and methods though share an interest in the cerebellum. Gall claims the cerebellum
governs amourness and reproductive instinct however Fluorens believes that the cerebellum is
responsible for coordinated movement. Gall's beliefs are grounded in his assumption that
psychological faculties correspond to localized cerebral organs whose development can be seen
on the surface of the skull. Flourens rejects this approach, arguing instead that the cerebellum
controlled coordinated movement, and that experimental ablation is the only reliable method for
determining brain function. Their disagreement of the matter does not just demonstrate opposing
views but reflects two completely different approaches in studying the mind. Where Gall's
approach relies heavily on correlation and morphology, Fluorens bases his theory using
experimental and causal procedures. The paper will begin by detailing Gall's process; Offering a
descriptive analysis of Gall's key assumptions, methods and conclusions regarding brain
localization. Fluorens’ conflicting assumptions will then be explored, along with an in depth
explanation of his experimentation on the cerebellum. Finally both positions will be critically
evaluated, arguing that Fluorens’ method provides much stronger evidence than Gall’s claims as
they lack empirical grounding. Although Gall argues that the cerebellum is the organ that houses
amativeness, Fluorens demonstrates through systematic lesion experiments that it controls motor
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coordination. Fluorens critically analyzes causal functions and provides evidence and
explanation which Gall’s method of correlation observations lack.
Gall’s theory on brain localization begins with the assumption that the mind is divided
into multiple distinct faculties. He believes that each faculty is rooted in its own specific and
independently functioning part of the brain. Gall specifically draws attention to the cerebellum
noticing “a connection might exist between the functions of physical love and those parts of the
brain situated at the nape of the neck” (Gall et al., 1838, p.13-14). Gall maintains that the brain’s
shape determines skull shape thus variations in skull morphology can reveal differences in
psychological traits. He draws from this conclusion that the size of the region in the brain
determines the strength of the corresponding mental faculty. He further develops this with the
claim that the larger the region is, the more apparent the corresponding mental trait is. To appeal
to this Gall offers what he describes as “innumerable observations which afford “positive proof”
of size cerebral organ exerting a great influence upon the power of manifesting the faculty” (Gall
et al., 1838, p. 238). He notices a pattern that those with heightened sexuality display distinct
projections near the nape of the neck, which he interprets as evidence that the cerebellum is
larger and therefore more active in these individuals. This illustrates that Gall’s method relies
primarily on comparative observations of skulls and heads in relation to behaviour. This becomes
increasingly clear through his analysis that “Nothing resembling a cerebellum can be
distinguished in those animals which propagate without conjunction. In all creatures, on the other
hand, which copulate, we find a part of the brain placed immediately above the spinal marrow,
and occupying the situation which the cerebellum holds” (Gall et al., 1838, p.16) For Gall, this
structural regularity across species suggests a natural connection between the cerebellum and
reproductive instinct. He uses the consistent anatomical location as evidence that the organ itself
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has a reproductive function. The foundational principle that guides Gall is that scientists “should
confine [themselves] to the facts observed”. In other words, Gall considers basing theories only
on observations as valid and reliable evidence, hence why his methods rely on observations he
forms. He reports that he “compared [the cerebellum’s] size during life with the energy of the
instinct of reproduction” (Gall et al., 1838, p. XVIII). The method here is correlational as he is
observing and comparing cerebellum sizes in individuals believed to possess strong sexual
drives. He measures their cranial features, and infers that any consistent morphological pattern
reveals a functional basis. Due to this commitment to observation Gall rejects experiment
insisting that their “effects [are] contradicted by the experiments of other practised investigators,
and which produce different phenomena every time they are made, whether on an animal or by
different physiologists” (Gall et al., 1838, p. 112). Gall's statement shows that he believes
experiments to be unreliable as he describes the findings as always varying thus not providing
concrete proof. Gall concludes that psychological functions are localized in discrete brain
regions and that the cerebellum specifically houses the sexual instinct. He believes he has found
consistent correlations between cerebellar size and reproductive behavior. Gall generalizes these
findings into a full theory of cerebral localization, claiming that personality traits, cognitive
capacities, and drives can be mapped onto specific points of the brain’s surface. Though the
evidential basis for this theory is entirely dependent on observations of morphology.
Alternatively, Fluorens begins with the belief that the mind is a unified whole instead of a
collection of separate faculties. He argues that “there are not, therefore, different seats for the
different faculties, nor for the different sensations,” because “the faculty of feeling, of judging, of
willing anything… resides essentially in a single organ” (Flourens, 1846, p. 35). To support his
theory, Fluorens utilizes experimental results. He states “In order to follow out an observation, it
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must be traced to the very end, and we must accept all that it yields to our research” (Flourens,
1846, p. 40). This displays the importance Fluorens places on experimentation. According to
Fluorens, true observation analysis is followed by systematically altering brain structures and
observing the resulting behavioral changes.It shows that Flourens believes it is the only reliable
way to determine the function of a brain region, and that he considers mere observation to be
insufficient in establishing function. Flourens’ primary method is ablation where he surgically
removes o specific areas of the brain in living animals, typically dogs, and observes the
consequences. He emphasizes that he conducts these procedures while allowing animals time to
heal, ensuring that transient shock effects do not mislead him. Flourens reports that he “may cut
away, either in front, or behind, or above, or on one side, a very considerable slice of the
hemisphere of the brain, without destroying the intelligence” (Flourens, 1846, p.34). This
suggests to him that no single region of the hemispheres alone accounts for higher cognition. His
experiments reveal distinct patterns. When he removes the hemispheres, “the animal instantly
loses its perception; it no longer sees nor hears” (Flourens, 1846, p. 80). This indicates a global
role for the cerebral hemispheres in perception. By contrast, when he removes the cerebellum,
the animal loses “the principle that presides over the locomotion of the animal” (Flourens, 1846,
p. 88). Flourens consistently observes that cerebellar ablation produces severe motor
coordination deficits: animals stagger, fall, and perform jerky, unregulated movements. Crucially,
Flourens notes that sexual instinct remains intact even when the cerebellum is completely
removed. This directly contradicts Gall’s claim that the cerebellum houses amativeness. Flourens
concludes that the cerebellum plays no role in reproductive instinct. Based on systematic
experimentation, Flourens determines that the cerebellum is “the seat of the principle that
presides over the locomotion of the animal” (Flourens, 1846, p. 88). It regulates coordination and
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balance, not sexuality. His experiments consistently show that cerebellar damage impairs
movement but leaves reproductive behavior unaffected.
Gall and Flourens differ not only in their conclusions but also in the strength of their
assumptions, the reliability of their methods, and the credibility of their evidence. Gall’s
foundational assumption that each mental faculty has an independent brain organ, is neither
demonstrated nor testable by his own methods. Moreover, Gall’s belief that skull shape
accurately reflects brain structure is never empirically validated. Without verifying this
connection, his entire foundation of belief rests on an untested premise. However Fluorens does
test this, finding that “You can slice off a considerable portion of an animal’s brain, either in
front, behind, on one side, or on the top, without his losing anyone of his faculties. The animal
may, therefore, lose all that Gall calls surface of the brain, without losing any of his faculties.
Therefore it cannot be that the organs of the faculties reside at the surface of the brain.”
(Flourens, 1846, p.86). Through testing Gall finds when removing the surface of any area of the
brain all the faculties remain intact which directly invalidate Galls theory. This reveals that Gall’s
system is therefore circular as he figures distinct faculties, assumes corresponding organs, infers
their locations through skull observation, and then uses these observations to confirm his original
assumptions. Nothing in this chain provides causal evidence. Fluorens explicitly highlights this
when expressing that he is “well aware … what Gall means ; he says it, and reiterates it
throughout his work. He says it, but does not prove it.” (Flourens, 1846, p. 53). Fluorens
acknowledges that although Gall’s point is understood he offers no evidence to thoroughly prove
its validity. In contrast, Fluorens adopts a more rigorous empirical approach through controlled
brain ablation. His experiments isolate specific structures and directly observe the behavioral
consequences of their removal. This method allows him to determine causal relationships in a
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way Gall’s observations cannot. By removing the cerebral hemispheres and the cerebellum
separately, he identifies which functions are lost in each case and observes consistent patterns of
impairment. His attention to recovery time strengthens the reliability of his results; he recognizes
that immediate post-surgical behaviors may be misleading and therefore waits for animals to heal
before drawing conclusions. Through this carefully controlled method, he finds that cerebellar
removal consistently disrupts motor coordination while leaving reproductive instinct unchanged,
directly contradicting Gall’s claims. Despite the strengths of Flourens’ experimental method,
certain limitations remain. His commitment to the unity of mind leads him to infer that
psychological functions cannot be localized at all, a conclusion that does exceed the scope of his
evidence. The fact that animals retain some cognitive abilities after large lesions does not
necessarily imply that the mind lacks specialized regions altogether. It could instead reflect
compensatory mechanisms however that is also a phenomena unknown in his time. While
Flourens successfully refutes Gall’s specific claim about the cerebellum, his broader rejection of
localization is less well supported. When evaluating both thinkers together, Flourens’
conclusions about the cerebellum clearly rest on more substantial evidence. Gall’s assertions rely
on unverified assumptions and non-causal observations. Whereas Flourens demonstrates through
direct experimentation that the cerebellum is essential for coordinated movement rather than
sexual instinct. Given the limits of Gall’s correlational method and the rigor of Flourens’
physiological experiments, the most defensible conclusion is that Gall’s localization of
reproductive instinct lacks empirical support.
This paper has examined the assumptions, methods, and conclusions of Gall and
Flourens, arguing that Flourens’ experimental approach provides more reliable evidence about
cerebellar function than Gall’s morphological correlations. Gall begins with untested
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assumptions about mental faculties, relies on skull observations that cannot reveal true brain
structure, and infers localization without causal evidence. Flourens, in contrast, uses systematic
ablation to reveal that the cerebellum regulates coordinated movement rather than sexual instinct.
His method isolates causal function in a way Gall’s approach cannot. Yet Flourens’ broader
rejection of localization is too strong. His experiments do not rule out the possibility that some
psychological functions may be localized though that may have been hard to conclude during the
resources available at that time. Still, with respect to the specific debate over the cerebellum,
Flourens decisively demonstrates that Gall’s theory is unsupported. The Gall–Flourens dispute
highlights a turning point in the scientific search for the mind. It shows the transition from
speculative correlational reasoning to causal experimental physiology. While neither thinker
reached a fully accurate neuroscientific model, Flourens’ approach represents a crucial step
toward modern methods that prioritize controlled experimentation over morphological inference.
Their debate illustrates the enduring challenge of linking brain structure to behavior which is a
challenge that continues to shape neuroscience today.
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References
Fluorens, P. (1846). Phrenology Examined (C. De Lucena Meigs, Trans.). Hogan and Thompson.
Gall, F. J., Vimont, J., & Broussais, F.-J.-V. (1838). On the Functions of the Cerebellum (G.
Combe, Trans.). Maclachlan and Steward.