70* Notices of Memoirs — On Pneumatic Foramina. 



" The influence of the lungs on the vertebral column of a Dinosaur 

 as distinct from the air-cells may be, perhaps, inferred from the 

 elevated condition of the neural arch and upward direction of 

 transverse processes under which the lungs extended in such a type 

 as Dtplodocus, described by Professor Osboi'n and the late Dr. J. B. 

 Hatcher. It is reasonable to infer that the lungs were so large that 

 their intermittent upward pressure stimulated the growth of the 

 neuro-central suture to form the high neural arch ; but as they 

 were not confined by an unyielding envelope in the same way that 

 the carapace confines the lungs of tortoises, there is but little lateral 

 compression of the body of a vertebra as a consequence of absorption, 

 which was localized laterally about the pneumatic foramen. 



" All down the vertebral column in Diplodocus the vertebra are 

 excavated, and the lateral holes were termed by Dr. Hatcher pleuro- 

 central cavities. They have been well described in Ornithopsis. 

 Their distinctive feature is that in the dorsal region the lateral foramina 

 expand within the centrum into large chambers separated by a median 

 vertical longitudinal partition, and each is commonly divided into 

 unequal anterior and posterior parts by an imperfect vertical 

 transverse lamina of bone. Fi'om this primary lateral cavity bone- 

 cells commonly extend to the articular faces of the centrum and 

 other parts of the vertebra. This condition of the pneumatic 

 vertebrEe is only dissimilar to that of birds in its details. In no 

 existing animals except birds is a similar pneumatic structure found 

 in the vertebral column, and it is only known in connexion with 

 air-cells prolonged from the lungs. There is no fact to suggest that 

 the lungs themselves wei"e extended into the pleuro-central cavities 

 of Dinosaurs : such an idea is not consistent with the pneumatic 

 condition of the vertebras in the elongated neck and tail. But with 

 the general resemblance to the condition in the bones of birds it has 

 been inferred that the pneumatic pressure, which was persistent 

 enough to absorb the bone locally and laterally, was greater in 

 Dinosaurs than in bii'ds, because the cavities excavated are larger. 

 Although this pressure, judged by its effects, was most potent in 

 the dorsal region of the lungs, it also extended to the neck and tail, 

 as in certain birds. It is therefore inferred that no cause is known 

 except prolongation of air-cells from the Inngs into the bones which 

 is capable of producing these results, for from no other source in nature 

 is the pressure derived which penetrates in this way into the skeleton. 



"This is inductive evidence from physiology and comparative 

 anatomy. In place of it Professor Osborn has offered nothing 

 except the following passage : — ' The dominating principle in 

 construction of the backbone is maximum strength with minimum 

 weight. The ingenuity of sculpture by which this is brought about, 

 every single vertebra differing from its fellow, baffles the 

 Lamarckian as well as the Darwinian, and tempts us to revive the 

 old teleological explanation.' ^ Teleology is not known as an 

 element in science, and explains nothing." 



1 Memoirs American Museum of Natural History, vol. i, part 5, p. 193» 

 " A Skeleton of Diplodocus.^' 



