Solothurn, 1842.

[217] Mueller's _Archiv_ for 1843, p. ccxlviii.

[218] _Untersuchtingen ueber die Entwickelung der
Wirbelthiere_, Berlin, 1850-55.

[219] Delivered 17th June 1858. Reprinted in _The
Scientific Memoirs of T. H. Huxley_, edited by M. Foster
and E. Ray Lankester, vol. i., pp. 538-606 (1898).

[220] _Cf._ Reichert, _supra_, p. 149.

[221] The origin of the pituitary body from the roof of
the mouth was first described by Rathke (1839).

[222] _Human Osteogeny explained in two Lectures_, London,
1736.

[223] _De capitis ossei Esocis lucii structura singulari.
Dissert. inaug._ Regiomonti, 1822.

[224] "Ueber das aeussere und innere Skelet," Meckel's
_Archiv_, pp. 327-76, 1826.

[225] _Vergl. Entwick. d. Kopfes d. nackten Amphibien_ (p.
186).

[226] _Arch. f. mikr. Anat._, xi., Suppl., 1874.

[227] "Om Primordial-Craniet," _Foerhandlingar Skand.
Naturf. Moele_, Stockholm, 1842.

[228] Vol. I., General part, pub. 1844.

[229] _Entosphenoid_, Owen.

[230] _Zweiter Bericht zootom. Anstalt zu Wuerzburg_, 1849.

[231] _Zeits. f. wiss. Zool._, ii., pp. 281-91.

[232] Mueller's _Archiv_ for 1849, pp. 443-515.

[233] _Zeits. f. wiss Zool._, ix., 1858.

[234] _Entw. d. Wirbelthiere_, pp. 139-40, 1861.

[235] _Lectures on the Elements of Comparative Anatomy_.

[236] _On the Archetype of the Vertebrate Skeleton_, p. 5,
1848.

[237] _System der thierischen Morphologie_, Leipzig, 1853.

CHAPTER XI

THE CELL-THEORY.

With the founding of the cell-theory by Schwann in 1839 an important
step was taken in the analysis of the degrees of composition of the
animal body. Aristotle had distinguished three--the unorganised
material, itself compounded of the four primitive elements, earth and
water, air and fire, the homogeneous parts or tissues and the
heterogeneous parts or organs, and this conception was retained with
little change even to the days of Cuvier and von Baer. Those of the old
anatomists who speculated on the relations of organic elements to one
another were dominated by Aristotle's simple and profound
classification, and proposed schemes which differed from his only in
detail. Bichat enlarged and deepened the concept of tissue, but the
degree of composition below this was for him, as for all anatomists of
his time, a fibrous or pulpy "cellulosity," living,