Notes, ii. i. 155 



7. The final cause must exist in conception before the stractures which are made with 

 a view to it. The whole organism therefore exists ideally before the orgfans, and these 

 again before the tissues, and these latter before their physical constituents. But actually 

 or materially the order is reversed. The physical constituents are the first to be produced ; 

 then from these are generated the tissues, and lastly from these the organs. And similar 

 sequences, ideal and actual, occur in the development of other than animal bodies, in 

 plants for instance, in works of art, etc. If, therefore, we have before us the order of 

 genesis, that is of actual evolution, we have merely to invert it to get the order of final 

 causes. The fact, then, that the tissues ar;2 evolved after their component substances 

 shows that the latter exist for the sake of the former, and the fact that the organs are 

 evolved after the tissues shows that the tissues are for the sake of the organs. 



8. The first degree of composition was that of the compound substances ; the second 

 that of the tissues ; the third that of the organs. The evolution, then, of an individual 

 organ has reached its final term when this third stage is attained. But in an animal or 

 a plant, as a rule, there is yet a fourth degree of composition. For the entire organism 

 is made up of a multiplicity of organs. This, however, is not the case with all organisms. 

 The simpler kinds (Aristotle would probably have instanced the Sponge, the Actinia, 

 the Medusa and, among plants. Lichens and Fungi) present no such distinction of parts, 

 as allows us to say that they are made up of organs. They are constructed not of 

 organs, but directly out of tissues. Their evolution, therefore, as that of a single organ, 

 ends with the third degree of composition. They are aggregates of the third not of the 

 fourth degree. 



'9. Having distinguished the homogeneous parts or tissues from the heterogeneous parts 

 or organs, A. proceeds to enquire why these latter are made out of the former, and ascribes 

 it partly to necessity, partly to a final cause. In the first place no other arrangement is 

 possible. The heterogeneous can only result from a combination of homogeneous 

 parts ; while the homogeneous cannot possibly be constructed from the heterogeneous. 

 Secondly, an organ is often used for several distinct offices ; and therefore requires distinct 

 properties. But its properties are those of the tissues which compose it, and therefore 

 it requires to be made of several tissues, seeing that each tissue has but one main 

 property. A. apparently confuses the properties of an organ with its functions. The 

 properties of an organ are doubtless the resultant of the properties of its component 

 tissues ; but the functions of an organ depend on more than this, namely on the relations 

 and structural connections of the organ as a whole with other parts. The properties of 

 a muscle, for instance, are' doubtless the resultant of the properties of the various tissues 

 that enter, into the composition of a muscle. The chief of these being muscular tissue, 

 and the main property of this being contractility, the main property of the whole 

 muscle is contractility ; and this property attaches to it whatever be its situation. But 

 the function of the muscle is to produce a certain definite motion of some part of the 

 body, and for this are required not merely the property of contractility but certain definite 

 attachments to the bones or other parts that are to be moved. 



10. A. had not the slightest suspicion of the contractility of muscle or, as he called it, 

 flesh ; the main purpose of this substance being in his opinion to serve as a medium for 

 the sense of touch (cf. ii. 8, Note 2 ; ii. lo, Note lo). Still less therefore could he have 

 any notion that a limb is. flexed or extended, accordingly as this or that part of the fleshy 

 mass about it contracts. He therefore apparently attributes extension and flexion to the 

 presence in the limb of diff'erent properties, one extensibility, the other flexibility ; these 

 properties being derived by the part, each from a different tissue. But he does not 

 attempt to state what these tissues may be. . 



