720 REPOET 1881. 



tive position of the body of air-breathers to the ground they stood or moved upon,' 

 and the criterion which Cuvier adopted to determine these aspects in the notable 

 controTersy with Geofiroy St. Hilaire, in 1830. That criterion was the 'cerebrum' 

 in Vertebrates, and its homologue, the 'supra-cesophageal ganglion,' in Invertebrates. 

 Cuvier exclusively applied the term ' brain ' {ceireaii) to this part of the cerebral 

 centres; moreover, he expressly rejects the homology of the spinal chord of Verte- 

 brates with the ganglionic chords of the body in Invertebrates. 



In an enlarged copy of the diagram by which Cuvier illustrated his position, the 

 author pointed out the grounds on which the great Comparative Anatomist con- 

 cluded that, however his opponent might turn about his articulate or molluscous 

 subject, the so-called ' brain ' would be on opposite sides of the alimentary canal. 



Now, to reconcile tl is difference it only needs to add to Cuvier's diagram of the 

 brain of the mammal the conario-hypophysial tract ; and, if the facts and deductions 

 in the present paper were allowed to be valid, the actual diiference would lie in the 

 atrophy of the embryonal homologue of the Invertebrate gullet and mouth in the 

 ■ Vertebrates, and tlie establishment in them of a new entry to the alimentary cavity. 

 In the Vertebrate embryo this anterior entry makes its first appearance as a capa- 

 cious branchial or water-breathing organ, and traces of this destination are deter- 

 minable in the higher Vertebrates, in \vhicli the respiratory function is, ultimately, 

 otherwise located and is performed in relation to an aerial medium. 



Eetm-ning to the criterions of the dorsal and ventral aspects of the animal body, 

 the author, with, he believed, all fellow-labourers in Homological Anatomy, main- 

 tained that the ganglionic body-chord in Invertebrates did answer to the myelon of 

 Vertebrates, and that, with the totality of the brain, the so-called 'neural axis' 

 was determined. So determined, he held that its position was the true criterion of 

 the dorsal or ' neural aspect ' of the body, whether the animal moved with it next 

 to or farthest from the ground, or neither the one nor the other, as in the human 

 pedestrian. The part or aspect of the body opposite the neural one was characterised 

 by the location of the centre, or chief centres, of the vascular system, and this had 

 led Professor Owen, at the commencement of his anatomical teaching, to term it 

 the ' haemal aspect.' 



Referring, finally, to the diagram of the Invertebrate and Vertebrate animals in 

 •corresponding positions, agreeably with the above criterion, the author showed that 

 the so-called 'brain' (Cuvier), or the supra-oesophageal brain-mass, of ('Omparative 

 Anatomy, was not above, but beneath, the mouth and gullet in Invertebrates, and 

 that the ' sub-oesophageal mass ' was above the mouth and gullet ; also that the 

 reverse relative positions were due to the atrophy of the primitive homologues of 

 such entry in Vertebrates, and the substitution of another opening and conduit to 

 the stomach ; whereby these anterior openings and conduits are on the lower or 

 ■' htemal ' side of the cerebrum in Vertebrates, but on the upper or neural side of the 

 ' cerebrum' or fore-brain in Invertebrates. Hence, the one division may be said to 

 be ' hsemastomous,' the other division to be ' neurostomous.' But their common 

 Ian, or ' unitj' of composition,' was vindicated by the embryonal phenomena. 



The paper was illustrated by drawings of the principal structures described, of 

 which drawings enlarged diagrams were exhibited to the Section. 



2. On the Acetabulum of Animals in which the Ligamentum Teres is de- 

 scribed as wanting. By Professor Struthees, M.D. 



In man, the four-cornered bony recess, occupied by fat, in the floor of tlie aceta- 

 bulum is exactly adapted to receive and cushion the ligamentum teres in the various 

 movements of the hip-joint. In birds, the equivalent of the recess is a well-defined 

 thin portion of the membrane which occupies the deficiency in the floor of the bony 

 acetabulum. The modifications presented by the cotyloid notch, passage, and i-ecess 

 in mammals possessing the ligament, are, as in man, adaptations to the position, 

 direction, and size of tlie ligament. In the hippopotamus the bony acetabulum 

 seems incompatible with the existence of a ligamentum teres. 



