EE VIEWS. 
347 
The several divisions of the frame are dealt with separately, ample reference 
being made under each head to the modifications which the more common 
anatomical features undergo in particular species. Under the sections of 
Osseous, Muscular, Nervous, Digestive, Absorbent, Circulating, Respiratory, 
Secretory, Tegumentary, and Generative systems, we have an exhaustive 
account of the general and microscopic anatomy of birds. Finally, the 
chapter on development deals with the history of the bird from its commence- 
ment as a minute germ hardly bigger than a pin’s point, to the period when it 
emerges from its calcareous prison. In the treatment of the Mammalia 
the same admirable method has been adopted, and in a few examples a more 
abundant supply of details has been given ; this is particularly true of the 
Quadrumana. In his classification of mammalia, Professor Owen adheres to 
his brain-scheme laid down in the Reade’s Lecture of 1859. He divides 
mammalia into four sub-classes: — Archencephala, Gyrencephala, Lissencephala, 
and Lyencephala. In his definition of these groups the author has modified 
his original opinions, and has granted the accuracy of Messrs. Huxley’s, 
Rolleston’s, and Flower’s observations. In his Reade’s Lecture he stated that 
in the Archencephala, which included man only, the cerebrum extended com- 
pletely over the cerebellum, so as to conceal it from view when the brain was 
looked on from above. He also contended that this character of the cerebrum 
at once served to distinguish man from all the Quadrumana. The researches, 
however, of Huxley and several other distinguished observers went to show 
that man’s brain is not peculiar in the respect alleged by Professor Owen, 
but that in various Quadrumana the cerebrum covers in the cerebellum, so as 
to prevent the latter from being viewed from above. Professor Owen also, 
at the date we refer to, denied that in the sub-class Lyencephala there was 
any corpus callosum uniting the two hemispheres of the brain. The subject 
was afterwards taken up by Mr. Flower, Curator of the Museum of the 
College of Surgeons, who showed very clearly that a remnantory or rudi- 
mentary corpus callosum is to be found in various marsupials. Professor Owen, 
therefore, as we have said, slightly changes the definitions formed in 1859, and 
gives the following as the characters of the mammalian sub-classes. “ When 
the hemispheres are connected by the 1 round commissure ’ and 1 hippocampal ’ 
commissure only .... the cerebral lobes are usually without folds, and 
have the cerebellum, olfactory lobes, and optic lobes exposed. The sub-class 
so characterized L is called Lyencephala.” The next stage is when the corpus 
callosum is present, but yet connects cerebral lobes which are very little 
superior in organization to those of the preceding sub-class ; the surface of 
the brain is smooth, or exhibits a few folds similar to those of the Lyen- 
cephala. “ The hemispheres leave the cerebellum and part of the olfactory 
lobes exposed. The sub-class so characterized is called Lissencephala .” 
Gyrencephala is the name given by Professor Owen to the next group in his 
classification. It is known by the possession of convolutions and a cerebrum, 
which is of large relative size, and which extends over half of the cerebrum and 
of the olfactory lobes. Finally, the sub-class Archencephala, which is formed 
for the reception of the genus Homo only, is described as having a cerebrum 
which not only completely covers the cerebellum and olfactory lobes, but 
extends “ in advance of the one and further back than the other.” Professor 
Owen’s admissions that the cerebrum does cover the cerebellum in some 
2 B 
YOL. V. — NO. XX. 
