478 NOTES 



185 The muscles of the heart and gullet are striped. In the lower ani- 

 mals these distinctions of voluntary and involuntary, striated and smooth, 

 solid and hollow, muscles can seldom be made. 



136 The skeleton of the carrion crow, for example, weighs, when dry, 

 only twenty-three grains. 



137 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 twenty-eight beats per second with its wings, while the bee makes 

 one hundred and ninety, and the house fly three hundred and thirty. The 

 swiftest race horse can run at double the rate of the salmon. So that 

 insect, bird, quadruped, and fish, would be the order according to velocity 

 of movement. 



138 The theory that flies adhere by atmospheric pressure is now aban- 

 doned. 



189 More precisely, the term brain applies only to the cerebrum, while 

 the total contents of the cranium are called encephalon. 



140 The exact functions of the cerebrum are not yet clearly understood. 

 If we remove 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, but not consciousness. 



141 It is very difficult to define sensation, or sensibility. The power is 

 possessed by animals which have neither nervous system nor consciousness. 

 These low manifestations of sensibility are called irritability the power- 

 by which an animal is capable of definitely responding to a stimulus from 

 without. The response is not called out by the direct action of the stimu- 

 lus, but is determined mainly by the internal structure and condition of 

 the animal. 



142 Parts destitute of blood vessels, as hair, teeth, nails, cartilage, etc., 

 are not sensitive. 



143 Tentacles " and " horns " are more or less retractile, while antennae 

 are not, but are hollow. Antennae alone are jointed. 



144 In man, the soft palate and tonsils also have the power of tasting. 



145 No organ of hearing has been discovered with certainty in the 

 radiates and spiders. The " ear " of many lower animals is probably an 

 organ for perceiving the animal's position rather than sound an " equi- 

 librium organ." 



146 It is wanting in the aquatic mammals. Crocodiles have the first 

 representative of an outside ear in the form of two folds of skin. 



147 This, like the definition of smell and hearing, is loose language. 



