366 ORGANSYSTEMSOFMAN 



Man is no longer at home in the trees but It requires only a slight knowledge of the 



has taken up life on the ground and with subject to realize that most of the informa- 



it the bipedal method of locomotion, a tion about the functioning of the human 



method far from new since the great camiv- body can come only through such experi- 



orous dinosaurs also employed it. Other ments. How would anyone suffering from 



present-day bipeds such as the ostrich can appendicitis, for example, particularly an 



easily outstrip him in cursorial travel. He is antivivisectionist ( the self-styled name ap- 



poorly fitted for life in the water where his plied to these people ) , appreciate having 



appendages are not well adapted for loco- a doctor who has had no experience what- 



motion. He can submerge for only very short ever on lower animals attempt to remove 



periods without coming up for air, and in the offending organ? If the antivivisection- 



cold water his survival time is very short, ist lived up to his code, he should rightly 



He has, however, one crucial organ that refuse any medication which stemmed from 

 accounts for most of his success, his well- a study of lower animals. However, it is 

 developed brain. This organ, by its intricate highly probable that if he is taken ill he will 

 disposition of nerve impulses, has made it proceed with all haste to obtain the best 

 possible for man to compensate for all of his available skill, no matter how it was ac- 

 physical deficiencies. With it he has been quired. Such groups today are only a gen- 

 able, through the power of speech, to com- eral nuisance, although they frequently 

 municate with his fellows and later to put cause the loss of valuable research time of 

 words down in writing. Over a long period prominent biologists who must stoop to the 

 of time this type of specialization has finally task of defending themselves. Much more 

 "paid off" because man today is the domi- could be said on the topic but perhaps 

 nant species on the earth. at this point it would be well for the student 



In order to understand man it has been to draw from his own experiences and form 



necessary to study other forms of animal his own conclusions about this matter, 

 life. Man does not lend himself well to ex- We shall now turn to a discussion of the 



perimentation for obvious reasons and, fur- organ systems of man, as illustrative of ver- 



thermore, he grows too slowly to permit tebrate organ systems in general. Each sys- 



studying succeeding generations. He can- tem will be discussed at some length, 



not be kept under the controlled conditions together with a brief account of similar 



that are possible with rats in a cage. How- structures in other animals from the lowest 



ever, most of our information about his to the highest. Although some attention has 



functioning has come through the careful been paid to these topics in the discussion 



study of lower animals. If it were not for of each animal group, it is well to review 



these experiments our knowledge would be tlie information briefly before each system 



very meager. This brings up an interesting of man is studied. With this approach, per- 



and important point concerning attitudes of haps the structures and their functions as 



the species, Homo sapiens. found in the human body may be better 



There are small isolated groups of people understood, 

 who oppose any animal experimentation 



( primarily experiments on dogs, cats, and OUTER COVERING-THE SKIN 



other pet species), sincerely, perhaps, or 



stirred by some ulterior motive such as pub- As we have seen in the preceding chapter, 



licity, for example. In any case, they are a all animals are provided with an exterior 



small but usually active group who are covering that functions as a barrier against 



constantly stumping for legislation which the outside world. This is extremely simple 



would curtail present-day experimentation, in the lower invertebrates, but becomes 



