March 16, 1900.] 



SCIENC:^. 



419 



writer proposes to draw attention more es- 

 pecially to the free sensory endings in vis- 

 cera, and to emphasize the following points '■ 



(1) the repeated division of such sensory 

 nerves before losing their medullary sheaths; 



(2) the relatively large number of arboriza- 

 tions in which such nerves terminate ; and 



(3) the fact that they terminate in the 

 mucosa and epithelium lining the hollow 

 organs and ducts. 



Sensory nerve terminations in the tendons of the 

 extrinsic eye muscles of the cat : Dr. Huber. 

 Marchi, Ciaccio and Sherrington have 

 shown that medullated nerve fibers termi- 

 nate in the tendons of the extrinsic eye 

 muscles of a number of mammals. These 

 nerves are looked upon as sensory nerves, 

 although, as Sherrington has shown, not 

 branches of the ophthalmic division of the 

 trigeminus. In the cat the nerves ending 

 in the tendons of the extrinsic eye muscles 

 do so in terminations which diiFer in 

 structure from the neuro-tendinous endings 

 found in other skeletal muscles of this ani- 

 mal. The medullary nerves which termi- 

 nate in the eye muscles of the cat lose their 

 medullary sheaths just before reaching their 

 destination and end in a network of varicose 

 fibers, which network surrounds the tendon 

 fasciculi just distal to the insertion of the 

 muscle fibers. Each tendon fasciculus sur- 

 rounded by such a plexus is enclosed within 

 a thin, closely fitting, fibrous sheath. 



Comments upon the figure of the mesal (^median) 

 aspect of a human hrain as published by Sis 

 and reproduced by him and others : Db. 

 Wilder. 



" In the Archiv fur Anatomic for 1893, 

 Professor His published a figure of the 

 mesal aspect of an adult human brain ; it 

 was reproduced on p. 76 of the protocols of 

 the B. ISr. A., and in the B. JST. A. itself, 

 Archiv fur Anat., 1895, Suppl. Band., p. 161, 

 but is there stated (evidently through in- 

 advertence) to represent a fetal brain of the 



third month. The figure has been repro- 

 duced without comment by Van Gehuchten 

 (second edition) and Barker ('The Kervous 

 System,' 1899, Fig. 92). Even if designed 

 merely as a diagram in illustration of its 

 author's views of the definitive segments, 

 and even if many teachers and investiga- 

 tors are so well informed as not to be mis- 

 led by its errors of omission and commis- 

 sion, certain features are certain to cause 

 serious and wide-spread misapprehension. 

 Twenty such features were specified. The 

 most important exemplify the general de- 

 fect of such figures in most manuals, viz., 

 incomplete circumscription of the cavities, 

 and inadequate demarcation of the cut sur- 

 faces from the natural (pial or endymal). 

 In these respects anatomists may well imi- 

 tate the accuracy of Reichert (' Der Bau 

 des menschlichen Gehirns,' 1859-61), al- 

 though his figures are not absolutely perfect. 



If an ' Isthmus Rhombencephali ' ivhy not an 

 ' Isthmus Prosencephali ' f Dr. Stroud' 

 Cornell University. 



" In the early fetal brain of man, the cat, 

 and perhaps some other mammals, there is 

 a necklike region just caudad of the mesen- 

 cephal. Professor Wilhelm His names this 

 region ' Isthmus Rhombencephali,' and ap- 

 parently regards it as coordinate with the 

 other five definitive segments recognized by 

 \i\vsY {Archiv. fur Anatomie, 1893, 173-174; 

 1895, Suppl. Bd. ' B. N. A.,' 157). But in 

 these same specimens, and in many of the 

 figures published by His in the Archiv for 

 1892 and 1893, and in 'Die Entwickelung 

 des menschlichen Rauteuhirns, ' 1891, there 

 is another necklike region cephalad of the 

 mesencephal quite as distinct and some- 

 times more so. A schema of encephalic 

 segmentation should be consistent, and 

 while not denying the possibility that one 

 or both of these regions may represent a 

 primitive neuromere, it seems reasonable 

 to conclude that, taking into account the 



