DR. CARPENTER S ZOOLOGY. 
53 
bellum, but they extend in advance of the one, and further back than the other. Their 
posterior development is so marked that anatomists have assigned to that part the cha¬ 
racter of a third lobe ; it is peculiar to the genus Homo, and equally peculiar is the ‘ pos¬ 
terior horn of the lateral ventricle,’ and the ‘hippocampus minor,’which characterize the 
hind lobe of each hemisphere. The superficial gray matter of the cerebrum, through the 
number and depth of the convolutions, attains its maximum of extent in man. Peculiar 
mental powers are associated with this higher form of brain, and their consequences 
wonderfully illustrate the value of the cerebral character ; according to my estimate of 
which, I am led to regard the genus Homo as not merely a representative of a distinct 
order, but of a distinct sub-class of the Mammalia, for which I propose the name of 
Archencephala.” 
Having thus accurately defined these four sub-classes, in each of 
which certain anatomical characters accompany the several varieties of 
cerebral structure, Professor Owen enters upon the question of their 
subdivision into secondary groups or orders. In most modern works 
on zoology the Mammalia are divided into twelve orders, and the grade 
which they occupy in regard to cerebral development is generally 
stated to be somewhat as follows:—I. Bimana, II. Quadrumana. III. 
Cheiroptera. IV. Insectivora. V. Carnivora. VI. Cetacea. VII. 
Pachydermata. VIII. Ruminantia. IX. Edentata. X. Rodentia. 
XI. Marsupialia. XII. Monotremata. Such is the scale given in Dr. 
Carpenter’s book. The opinions of Professor Owen are by no means in 
accordance with these; the Mammalia being by him divided into fifteen 
orders, and several of these are assigned a position in the scale of organi¬ 
zation far different from that which they are usually said to occupy. 
The sub-class Lyencephala includes two orders, Marsupialia and 
Monotremata. Thus, the true position which the Implacentalia bear 
to the other Mammalia is now for the first time clearly defined. Zoo¬ 
logists have long felt that the Marsupialia are of more importance than 
any other single order of the class (with the exception of Bimana), 
though at the same time they ought not to form a group parallel with 
the Placentalia. The utility of Professor Owen’s views, in thus indi¬ 
cating the four subtypes which exist in the Mammalia, is here strikingly 
manifest. 
The Lissencephala are divided into four orders, viz., Rodentia, In¬ 
sectivora, Cheiroptera, and Bruta (Edentata). Two of the groups here 
included are, as we have seen, generally assigned a rank among qua¬ 
drupeds, second only to that of the Quadrumana. Professor Owen, in 
opposition to the views of M. Gervais and Milne Edwards, traces the 
connexion between the Insectivora and certain of the Marsupials, and 
considers the Cheiroptera (with a few exceptions) as volant Insectivora. 
Certain other peculiarities in structure and habit indicate, in the opi¬ 
nion of Professor Owen, the low grade of the Lissencephala, such as the 
permanent irritability of muscular fibre among the sloths; the long, 
slender, beak-like edentulous jaws and gizzard of the Anteaters; the 
quills of the Porcupine and Hedgehog; the aptitude of the Cheiroptera, 
Insectivora, and certain Rodentia, to fall, like reptiles, into a state of true 
torpidity, associated with a corresponding faculty of the heart to circu¬ 
late carbonized or black blood. 
