•72 ORIGINAL ARTICLES. 



himself, and by my own personal observations. The third rests upon 

 the evidence of Messrs. Schrceder van der Kolk and Yrolik, and of an 

 eminent countryman of our own, Dr. Allen Thomson, to whom I am 

 indebted for unpublished observations made with express reference to 

 these very points. 



1. The third lobe or posterior lobe of the cerebrum. — Many ana- 

 tomists divide the cerebral hemispheres of man into only two lobes, the 

 anterior and the posterior, separated from one another by the fissure of 

 Sylvius ; but it is more usual to speak of three lobes, * an anterior, a 

 middle, and a posterior, the latter, or ' third lobe,' being the posterior, 

 inasmuch as it consists of the hinder part of that, which those who 

 divide the cerebral hemispheres into two lobes, call ' posterior.' It is in 

 this sense that Cuvier, Meckel, and Tiedemann use the term third, or 

 posterior lobe. It is generally admitted that no very strict line of de- 

 marcation is traceable between the middle and posterior lobes ; ana- 

 tomists being content to accept Cuvier' s curt definition : — 



" La partie du cerveau situee au-dessus du cervelet est ce qu'on 

 nomme le lobe posterieur du cerveau. "f 



So far as I am aware, the terms " third" or "posterior lobe," have 

 never been applied in any other senses than those which I have indicated. 

 Under these circumstances, it is utterly incomprehensible to me how any 

 one competently informed, either with respect to the literature or to the 

 facts of the case, can assert that the hind lobe "is peculiar to the genus 

 Homo ;" for not only will the inspection of any ape's brain convince one 

 of the contrary, but the facts were originally ascertained and published 

 by a most competent authority, and have never been doubted for nearly 

 forty years. 



Tiedemann' s " Icones Cerebrorum Simiarum," published in 1821, in 

 fact, ought to be familiar to every student of mammalian anatomy. On 

 turning to his first Plate, one finds the first figure to be a representation of 

 the brain of " Simla nemestrina" The explanation of the figures says : "a, 



* It is not a very easy matter to determine with whom these divisions originated. 

 Vesalius (Humani Corporis Fabrica, libri septem, MDCXLII.) speaks neither of lobes 

 nor of special ' prominentia?' in the cerebral hemispheres, though he describes them very 

 accurately, explaining particularly that the under surface of these hemispheres is adapted 

 to the ' tubera' of the cranial bones. 



"Varolius (Anatomise sive de Resolutione Corporis Humani, libri iii., MDXCT. p. 

 131) says, in his letter to Hieronymus Mercurialis : ' De nervis opticis multisque aliis 

 praater communem opinionem in humano capito observatis ;' 



" Sunt autem tres cerebri prominentia? : anterior, media, et posterior 



postrema cerebri prominentia replet cavitatem productam a. superiori parte occipitii a. 

 posteriori ossis sincipitis et ossis petrosi.' 



This looks like the origin of the division into three lobes, while Willis seems to 

 have originated the division into two. 



" Porro in homine cui cerebrum prae ceteris animalibus capax et amplum est, utrum- 

 que haemisphaerium rursus in duos lobos nempe anteriorem et posteriorem subdividitur: 

 inter quos arteriae carotidis ramus, utrinque instar rivi limitanei productus eos veluti in 

 binas provincias distinguit " — Willis, Cerebri Anatome, 1664. 



f Lemons d'Anatomie Comparee, 2de ed., tome iii., p. 44. 



