350 
POPULAR SCIENCE REVIEW. 
reprinted his fine monograph upon the Crested Agouti. His investigation of 
the Dasyprocta cristcita was conducted jointly with Dr. J. Murie, of the 
Zoological Society, and the facts arrived at may be thus briefly stated : (1) 
The unconstricted condition of the stomach of D. cristata, as compared with 
that of D. aguti j (2) the tendency towards a double apex of the heart ; (3) 
the approximation of the ureters to the fundus of the bladder,- (4) the presence 
of a superficial long femoral artery. As regards the comparison between the 
crested Agouti, guinea-pig, hare and rabbit, Messrs. Mivart and Murie find 
that the first differs from all the others and stands alone in the following 
particulars : (1) The number and arrangement of the pads of the pes and 
manus; (2) the greater extension of the levator clavicuke,- (3) the absence of 
the rhomboideus capitis muscle : 5, 6, 7, 8, 9, and 10, refer to peculiarities 
of other muscles, which we fear are unfamiliar to our readers. 
The Osteology of the Insectivora has also been very carefully studied by 
Mr. Mivart, but as the memoir in which his observations on this subject are 
stated appears in the May number of the Journal of Anatomy , we must refer 
our readers to that periodical for the particulars. 
The Movement of Flight in Birds , fyc., is the subject of a paper read in 
June last before the Linnean Society by Dr. J. B. Pettigrew. After pointing 
out the nature of the various forms of locomotion in animals, and showing 
the relation between the surface moved upon and the organs of locomotion, 
Dr. Pettigrew states that the body, or parts of the body, in all animals are 
presented and withdrawn from the several media by rotatory and spiral 
movements. These movements are for the most part produced by a judicious 
combination of ball-and-socket and hinge joints, the former occurring as a 
rule at the shoulder or pelvis, the latter in the limbs when present. The 
spiral movements are least perceptible in the extremities of land animals, 
but a careful examination, of the structure of the joints, particularly the 
elbow and knee joints, and of their movements, will convince even a casual 
observer of their presence. They are more marked in animals which swim, 
the sea-bear twisting its flappers about with incredible dexterity, so as to 
present them obliquely to the water the one instant, and non-obliquely, or 
with their thin edge, the next. The same happens in the lower portions of 
the body in the seal and fish, the latter applying its tail to the water very 
much as an oar in sculling. The rotatory and twisting movements are 
still more perceptible in the application of wings, the pinions of the 
insect, bat, and bird being for this purpose twisted upon themselves. Dr. 
Pettigrew attaches considerable importance to this circumstance, and shows 
that but for the spiral conformation of the wing, and the fact of its 
being rotated on and off the wind during extension and flexion, the air could 
not be rendered subservient to the purposes of flight. He further shows that 
the more the wing is twisted, and the greater the number of its oscillations, 
the greater is its elevating and sustaining power. It would, therefore, seem 
that the screw, or a modification of it, enters into the structure of the bodies 
and extremities of all vertebrates, and that these are presented to the land, 
the water, and the air by spiral movements whicn remarkably resemble each 
other. Dr. Pettigrew’s paper is illustrated by upwards of 70 original draw- 
ings, a large proportion of the figures being from living animals. 
Blood Corpuscles of the Two-toed Sloth. — Professor Jtolleston lately tested 
