MAMMARY GLANDS. 
III. Cheiroptera. 1V. Insectivora. V. Car- 
nivora. WI. Cetacea. VII. Pachyder- 
ma. VIII. Ruminantia. 1X. Edentata. 
X. Rodentia. 5 
Sub-Class—IMPLACENTALIA. 
XI. Marsupialia. XII. Monotremata. 
The aim of the subjoined table is to express 
245 
the mutual affinities and inter-dependencies of 
the several orders of Mammalia, rei points 
at which they are most nearly related to the 
inferior classes of the vertebrate animals. The 
annectant genera, some of which are extinct, 
are printed in italics, the orders and classes in 
Roman capitals. 
BIMaNa. 
QuADRUMANA. 
i] | 4 | | | 
Galeopithecus. Lemur. : Cheiromys. : 
Bradypus. Didelph YS. 
-CHEIROPTERA........ CARNIVORA........ | .......- RODENTIA...... MARSUPIALIA. 
Cu ie 
INSECTIVORA.... 
Otaria. 
CETACEA... 
Pterodactylus. — Ichthyosaurus. 
| 
AVES. PISCEs. 
MAMMARY GLANDS.—Syn. Les glandes 
mammaires, Fr., Die Milch, die Brust-drisen, 
Germ. These important organs of secretion 
are the peculiar characteristic of the highest 
division of the animal kingdom, Mammalia. 
Tn a physiological point of view they should 
be regarded as uterine appendages, as a por- 
tion of that series of instruments which Na- 
ture has provided in greater or less number, 
according to the ultimate perfection of the 
animal, for its gradual development. Their 
close proximity to the ovarian apparatus in 
some Mammalia, the cetacea for instance, and 
their peculiar structure and function in the 
Marsupiata, confirm this view of their phy- 
sidlogical character. It is interesting to trace 
how gradually they have been removed from 
their caudal position to the atlantal portion of 
the body, so that in the human species, where 
the instincts are subjugated to the control of 
reason, and the helplessness of the infant has 
_ been made the means of moral training to the 
_ mother, these organs are brought towards the 
anterior, the nobler portion of the body. 
_ _ It must not, however, be supposed that this 
_ change of position is sudden, any more than 
« 
_ any other step in the scale of progressive deve- 
lopment of organized beings. Formerly it was 
supposed that the re-connection of the ovum to 
the mother through the medium of bloodvessels 
collected into a placenta was as universal 
throughout the class Mammalia as the presence 
_ of these glands; but the careful researches of 
Professor Owen have proved that the Marsu- 
_ piata and most probably some of the Mono- 
_ tremata form an exception to this rule. The 
_ fact is interesting in reference to the present 
| Subject from the greater importance which is 
ra 
np © si MENTMEM SS coco s 
| aren 
Glyptodon. Toxodon. Moschus. 
e —J 
wes. .PACHYDERMATA,... RUMINANTIA. 
.. MonorREMA, 
eee ee eee 
RepTiLia. 
(R. Owen.) 
given to the mamma in consequence of the ab- 
sence of this vascular connection, and the addi- 
tion of accessory structures which are absent in 
the more perfect mammalia. 
The arrangement of the secreting membrane 
of mammary glands has been universally found 
to be vesiculated, the only difference in differ- 
ent classes of animals consisting in the extent 
of secreting surface, owing to differences in the 
size of the cells, and their greater or less concen- 
tration within a circumscribed space. This 
vesiculated structure was described in 1751 by 
Duvernoi* in the hedgehog (Trans. of the 
Petersburg Academy), and in the human spe- 
cies it was discovered by Cruikshank, and de- 
scribed in his work on the absorbent glands, the 
second edition of which was published in 1790. 
At page 209 his words are, “ The acini are 
small vesicles like Florence flasks in miniature ; 
in these, the arteries secreting the milk termi- 
nate ; and from these the excretory ducts, or the 
tubes carrying off the milk take their origin. 
The existence of such vesicles has been doubted ; 
Dr. Hunter doubted till my injections con- 
vinced him of the fact.” He then goes on to 
explain his ‘method of injecting, and concludes 
by saying that preparations exhibiting this fact 
may be seen in the anatomical collection in 
Great Windmill-street, which he had made 
fifteen years previously. 
Miiller, to whom the above fact was known, 
states that Mascagni recognised and demon- 
strated the vesicular ends of the lactiferous 
tubes and the absence of all direct commu- 
nication .with the bloodvessels, in his Pro- 
dromo della Grande Anatomia, Firenze, 1819. 
* Miller de gland. &c. 
