NOTES 473 



integuments of plants had been rendered perfectly transparent to our eyes, 

 the vegetable world would present a very different aspect from the apparent 

 immobility and repose in which it is now manifested to our senses." 

 HUMBOLDT'S Cosmos, i., 341. 



67 See Gray's " Structural Botany," 6th ed., Introduction ; also Rolles- 

 ton's " Forms of Animal Life," Introduction. 



68 " Life has been called the vital force, and it has been suggested that 

 it may be found to belong to the same category as the convertible forces, 

 heat and light. Life seems, however, to be more a property of matter in a 

 certain state of combination than a force. It does no work, in the ordinary 

 sense." Professor WYVILLE THOMSON. 



69 The vegetable cell usually consists of a cell wall surrounding the pri- 

 mordial utricle or protoplasmic sac. In animal cells the former, though 

 often present, is usually not easily seen. As a general fact, animal cells 

 are smaller than vegetable cells. 



70 Cells are not the sources of life, as once thought, but are the products 

 of protoplasm. " They are no more the producers of vital phenomena than 

 the shells scattered in orderly lines along the sea beach are the instruments 

 by which the gravitation force of the moon acts upon the ocean. Like 

 these, the cells mark only where the vital tides have been and how they 

 have acted." Professor HUXLEY. 



71 Many of the bones of the skull are preceded by membrane hence 

 called membrane bones, 



72 In the heart, the muscular fibers are striated, yet involuntary ; but the 

 sarcolemma is wanting. 



73 We may, however, infer that the animal functions are not absolutely 

 essential to the vegetative, from the facts that plants digest without muscles 

 or nerves, and that nutrition takes place in the embryo long before the 

 nerves have been developed. 



74 Scorpions and spiders properly feed upon the juices of their victims 

 after lacerating them with their jaws, but fragments of insects have been 

 found in their stomachs. 



75 The real tongue forms the floor of the mouth, and is found as a distinct 

 part in a few insects, as the crickets. 



76 In the cyclostomata, it is circular or oval. 



77 The mouth of the whale is exceptional, the walls not being dilatable. 

 The act of sucking is characteristic of all young mammals, hence the need 

 of lips. 



78 The ant-eater has two callous ridges in the mouth, against which the 

 insects are crushed by the action of the tongue. 



79 The baleen plates do not represent teeth ; for in the embryo of the 

 whale we find minute calcareous teeth in both jaws, which never cut the gum. 

 The whalebone is a peculiar development of hair in the palate, and under 

 the microscope it is seen to be made up of fibers which are hollow tubes. 



