L] GENERAL VIEW. 2l 



V. PHARYNGOBRANCHIL Containing only that headless, 

 heartless fish without red blood the Amphioxus or 

 Lancelet. 



FIG. 35--THE LAMPREY FIG. 36. THE LANCELET 



( Petromyzon). (A mplrioxus) . 



The foregoing list has been given to render comprehensible 

 the references to different animals which must be so often 

 given in the succeeding lessons. 



In those lessons the several parts and organs of man's 

 body will be examined and described, not only directly, but 

 also in the reflected light to be derived from a' knowledge of 

 the more remarkable conditions of .the same parts in other 

 animals. 



24. The organs of man's body may be divided into three 

 classes : 



I. Organs of Investment and Support (skeletal). 

 II. Organs of Motion and Innervation, i.e. Muscular and 



Nervous. Structures, and organs of special sense. 

 III. Organs of Sustentation, i.e. nutritive, circulating, re- 

 spiratory, and excretory structures. 



This division, however, is rather physiological than ana- 

 tomical, so that a more convenient classification (the one to 

 be adopted in the succeeding chapters) will be 



I. The Skeleton, both internal (endoskeleton} and external 



(exoskeletoti). 

 II. The Muscular Structures. 



III. The Brain and Nervous System. 



IV. The Organs of Sense. 



V. The Heart, Arteries, and Veins. 

 VI. The Alimentary Tube and its appendages, 

 VII. The Respiratory and Vocal Structures and the Excre- 

 tory Organs. 



