PJROMORPHOLOa Y. 



133 



IV. Promorphology, or Study of the Fuxdamextal Forms. 



Organic and Inorganic Bodies. — The structure of the individual 

 animal rests upon the regular combination of differently-function- 

 ing organs. The organs thus assume a relation to one another 

 which is definite for each animal group, or varies only in sul)ordi- 

 nate wavs. If the various groups be oomjoared with reference to 

 the principle of the arrangement of parts, there appear a few 

 fundamental forms which play a role in morphology similar to that 

 <if the fundamental forms of cr3'stals in mineralogy. But we must 

 not carrv this comparison too far, and attempt to compare the 

 studv of the fundamental forms, the 'prnmovphology, of animals 



FiG. s4.—,S'pfm(7f!;o;!t(ma(iiis, fresh-water sponge. (After Hii.xlfy.) a. superficial layer 

 witli dermal pores; /.ic, region of the ampullie; (/, osculum. 



with crystallograi^hy as of equal value. A crystal is a mass made 

 up of similar parts; its form is the necessary and immediate result 

 of the chemico-pliysical constitution of its molecules. A direct 

 connection of this kind between molecular structure and funda- 

 mental form does not, and cannot, exist in the organism, since 

 each organ is composed of many chemical combinations. C'onse- 

 quently there is lacking also the mathematical regularity which 

 occurs in crystals. Even in the case of animals which have the 

 greatest regularity in the arrangement of their parts there is not 

 an entire conformity to the demands of the fundamental form, so 

 that we are compelled to ignore certain greater or less variations. 

 If, for exam2ile, we call man bilaterally symmetrical, wo overlo(.)k 

 not only the slight asymmetry of a nose awry, etc., but also what 

 is more important — that the liver has been pushed to the right. 



