32 COMPARATIVE PHYSIOLOGY. 



ear, nose, tongue, and the entire surface of the hody — are faith- 

 ful reporters of facts. They put the inner and outer worlds in 

 communication, and without them all higher life at least must 

 cease, for the organism, like a train directed by a conductor that 

 disregards the danger-signals, must work its own destruction. 

 Without going into further details, suffice it to say that the pro- 

 cesses of the various cells are subordinated to the general good 

 through the nervous system, and that susceptibility of proto- 

 plasm to stimuli of a delicate kind which enables each cell to 

 adapt to its surroundings, including the influence of remote as 

 well as neighboring cells. Without this there could be no 

 marked advance in organisms, no differentiation of a pro- 

 nounced character, and so none of that physiological division 

 of labor which will be inferred from our brief description of 

 the functions of a mammal. The whole of physiology but 

 illustrates this division of labor. 



It is hoped that the above account of the working of the ani- 

 mal body, brief as it is, may serve to show the connection of 

 one part functionally with another, for it is much more impor- 

 tant that this should be kept in mind throughout, than that all 

 the details of any one function should be known. 



LIVING AND LIFELESS MATTER. 



In order to enable the student the better to realize the na- 

 ture of living matter or protoplasm, and to render clearer the 

 distinction between the forms that belong to the organic and 

 inorganic worlds respectively, we shall make some comparisons 

 in detail which it is hoped may accomplish this object. 



A modern wateh that keeps correct time must be regarded 

 as a wonderful object, a marvelous triumph of human skill. 

 That it has aroused the awe of savages, and been mistaken for a 

 living being, is not surprising. But, admirable as is the result 

 attained by the mechanism of a wateh, it is, after all, composed 

 of but a few metals, ete., chiefly in fact of two, brass and steel ; 

 these are, however, made up into a great -number of different 

 parts, so adapted to one another as to work in unison and ac- 

 complish the desired object of indicating the time of day. 



Now, however well constructed the watch may be, there are 

 waste, wear and tear, which will manifest themselves more and 

 more, until finally the machine becomes worthless for the pur- 

 pose of its construction. If this mechanism possessed the power 



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