510 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the tympanic and the squamosal, and forms at least a part of the 

 ligamentum anterius mallei, and that the next region in front has passed 

 between the condyle and the squamosal and become the articular 

 meniscus. 



Transition between Internal Iliac and Umbilical Arteries in the 

 New-born.* — E. Argand finds that the structural transition between 

 the hypogastric artery and the umbilical artery happens in the internal 

 half of the intra-abdominal part of the latter. The calibre of the vessel 

 progressively diminishes and the vascular walls thicken. This thicken- 

 ing seems to result from the formation of new longitudinal muscular 

 fascicles. The elastic layers of the media begin to resolve into extra- 

 ordinarily thin fibres. Then the internal elastic coat thins out and 

 fibrillates in like manner. The delimitation between the internal tunic 

 and the middle tunic becomes now very difficult, not to say impossible. 

 It is only by analogy with the structure of the other arteries in the new- 

 born that we consider the internal tunic as reduced to a vascular 

 epithelium backed externally by a very thin connective tissue. The 

 structural transformation of the umbilical artery begins near the hypo- 

 gastric by local thickening of the wall as a longitudinal ridge, at whose 

 level the artery is not long in presenting the characters seen in its extra- 

 abdominal passage. A second thickening now appears, all the vessel 

 thickens, and the structure of the umbilical artery is realised. 



Development of Nerve Fibres.f — A. von Kolliker champions the 

 view that all nerve-fibres in Vertebrates are direct protoplasmic out- 

 growths of peripheral or central nerve-cells, each nerve-cell giving rise 

 to not more than one nerve-fibre. What are called Schwann's cells, 

 within fused rows of which the nerve-fibres are believed by some to 

 arise, are mesodermic enveloping elements. Nerve-fibres usually end 

 freely, in any case, without direct connection with nerve-cells. This is 

 the doctrine of independent nervous units or neurons. It holds true for 

 Vertebrates, and probably for Arthropods and Molluscs. 



Hypochorda of Salamandra Maculosa.! — Ad. Eeinhardt finds that 

 this peculiar sub-notochordal rod arises in the salamander, as in all 

 other lower Vertebrates, from the endoderm. A trunk portion appears 

 first, then a caudal portion, and lastly a relatively rudimentary hypo- 

 chorda. Degeneration begins at the two ends, and the part first formed 

 — the anterior trunk portion — is the last to go. The degeneration is 

 quite complete. Nothing certain can be said as to its morphological or 

 phylogenetic import. 



Visceral Arches of Urodela.§ — L. Driiner completes his elaborate 

 account of the structure and development of the skeletal parts, the 

 musculature, and the innervation of the hyoid, branchial arches, and 

 laryngeal region of Urodela. He deals with Salamandra, Triton, 



* Journ. de l'Anat. et Phys., xl. (1904) pp. 298-304. 



t Anat. Anzeig., xxv. (1904) pp. 1-6. 



% Morpliol. Jahrb., xxxii. (1904) pp. 195-231 (2 pis.). 



§ Zool. Jahrb., xix. (1904) pp. 361-G90 (12 pis. and 44 figs.). 



