3874 NOTES. 
mals, the posterior limbs are generally most developed; in aquatic animals, 
the anterior. Dr. Wyman contends that the limbs are tegumentary organs, 
and attached to the vertebral column in the same sense that the teeth are 
attached to the jaws. 
89 The muscles of some Invertebrates, as Spiders, are yellow. 
90 The muscles of the heart and gullet are striped. In the lowest animals, 
these distinctions of voluntary and involuntary, striated and smooth, solid 
and hollow, muscles can seldom be made. 
%t The skeleton of the Carrion-crow, for example, weighs, when dry, only 
23 grains. 
°2 The Dragon-fly can outstrip the swallow, nay, it can do in the air more 
than any bird—it can fly backward and sidelong, to right or left, as well as 
forward, and alter its course on the instant without turning. It makes 28 
beats per second with its wings; while the Bee makes 190, and the House- 
fly 330. The swiftest Race-horse can double the rate of the Salmon. So 
that Insect, Bird, Quadruped, and Fish would be the order according to ve- 
locity of movement. 
°3 These suckers (pulvilli) have a delicate fringe of hairs, each hair being a 
minute tube containing a viscid fluid by which the Fly adheres. 
°4 The cilia of Infusoria appear to act independently of any nervous power. 
95 More precisely, the term brain, or brains, applies only to the cerebrum, 
while the total contents of the cranium are called encephalon. 
°6 The exact functions of the cerebrum are not yet clearly understood. 
If we remoye it from Fishes, or even Birds, their voluntary movements are 
little affected; while the Amphioxus, the lowest of Fishes, has no brain at 
all, but its life is regulated by the spinal cord. Such mutilated animals, 
however, make no intelligent efforts. The substance of the cerebrum, as 
also the cerebellum, is insensible, and may be cut away without pain to the 
animal; and when both are thus removed, the animal still retains sensation. 
"7 Parts destitute of blood-vessels, as hair, teeth, nails, cartilage, etc., are 
not sensitive. The impressibility of the nerves is proportioned to the activ- 
ity of circulation. According to the recent investigations of Dr. Bowditch, 
the channels of motor and sensitive impressions lie in the lateral, and not in 
the anterior and posterior, columns of the spinal cord. 
98 “Tentacles”? and ‘‘horns”’ are more or less retractile, while antennz 
are not, but all are hollow. Antenne alone are jointed. 
89 Tn Man, the soft palate and tonsils also have the power of tasting. 
100 No organ of hearing has been discovered with certainty in the Radiates 
and Spiders. 
101 Tt is wanting in the aquatic mammals. Crocodiles have the first rep- 
resentative of an outside ear in the form of two folds of skin. 
102 This, like the definition of smell and hearing, is loose language. There 
is no such thing as sound till the vibrations strike the tympanum, nor even 
then, for it is the work of the brain, not of the auditory nerve. Sound is 
the sensation of the wave-movement of the air, and hearing is that sensa- 
tion. So without eyes the world would be wrapped in darkness; light is 
nothing. 
103 In Invertebrates and aquatic Vertebrates, the crystalline lens is globu- 
