98 PROCEEDINGS OF THE AMERICAN ACADEMY 



I 



Balfour, F. M. 

 '80. A Treatise on Comparative Embryology. Vol. I. xi -+- 492 pp., 275 figs. 



London : Macmillan & Co. 

 '81. Same. Vol. II. xi + 655 + xxii pp., 429 figs. 

 Bidder, F., und Kupffer, C. 

 '57. Untersuchungeii iiber die Textur des Riickenmarks und Entwickelune 

 seiner Fornielcmcnte. viii + 121 pp., 5 Taf. Leipzig. 

 Foster, M., and Balfour, F, M. 

 '74. riie Elements of Embryology. Part I. xix + 266 pp., 71 figs. London : 

 Macmillan & Co. 

 Kolliker, A. 

 '61. Entwickelnngsgeschichte des Menschen und der hiJheren Thiere. vi + 



4G8 pp., 225 figs. Leipzig. 

 '79. Same. 2d edition, xxxiv + xvi + 1033 pp., GOG figs. Leipzig. 

 Loewe, L. 

 '80. Beitrage zur Anatomic und zur Entwickelungsgeschichte des Nerven- 

 systems der Saugethiere und des Menschen. Bd. I. Die Morphogenesis 

 des centralen Nervensystems. xiii+12G pp., 18 Taf. Leipzig. 

 Lubinoff. 

 '74. Embryologische und histogcnetische Untersuchungen iiber das sympa- 

 thetisclie und centrale cerebrospinal Nervensystcra. Virchow's Archiv 

 f. Physiol., Bd. LX. pp. 217-273, Taf. VII. and VIIL 

 Remak, Robert. 

 '55. Untersuciiungen iiber die Entwickclung der Wirbelthiere. vi + xxxviii 

 + 195 pp., 12 Taf. Berlin : G. Reimer. 1850, 1851, 1855. 

 Waldeyer, W. 

 '76. Ueber die Entwickelung des Centralkanals im Riickenmark. Virchow's 

 Archiv f. Physiol., Bd. LXVIII. pp. 20-26. 6 Holzschn. 



Nothing is said concerning the formation of the posterior fissure by 

 the earlier writers on the development of the nervous system. Even 

 Remak ('55) does not enter into this subject. 



Bidder and Kupffer ('57, p. 114) say that in the chick embryo, be- 

 tween the eighth and ninth days of incubation, the white substance of 

 the posterior columns has grown around the posterior segment of the 

 cord, so that only a small gap, the posterior fissure, remains between 

 the columns. They do not attempt to pursue further the process which 

 gives rise to this fissure. 



In the first edition of Kulliker's Entioickelungsgeschichte des Men- 

 schen, etc. ('Gl, p. 2G2), incidental to an account of the gradual ob- 

 literation of the dorsal part of the central canal, there is a short 

 description of cross sections of the cord at various stages in the devel- 

 opment of man, which affords some insight into the processes accom- 

 panying the formation of the posterior fissure. In human embryos of 

 about six weeks the central canal is diamond-shaped on cross section ; 

 its epithelium is of nearly uniform thickness except in the dorsal part. 



