i84 THEORETICAL BIOLOGY 



we may be in a position to determine exactly what are the 

 agreements and the differences. 



Let us take as an example a staircase built of bricks. It 

 is quite permissible to call the separate steps organs consisting 

 of a brick- tissue, made up of brick-cells. If throughout we 

 had only to deal with implements made of a uniform material 

 which, through various chemical and physical processes, took 

 on all possible shapes, colours and properties, the comparison 

 of organisms with implements would be striking. We should 

 find everywhere the same morphological basal element, an 

 element which we could compare with the cell, the elementary 

 building-stone of the organism. The same substances that 

 we recognise in different implements might be regarded as the 

 same fundamental tissue. This would also allow of our 

 regarding as organs the various parts of implements, even 

 where they consist of different substances. 



Now since there actually are different implements made of 

 the same original material treated in various ways (i.e. all 

 the things built up of bricks), if we are to institute a sound 

 comparison between organisms and implements, we must not 

 dismiss the attempt to imagine all implements reduced to 

 the like elementary denominator, the cell. On the contrary, 

 such an idea proves very valuable, because after eliminating 

 everything unimportant, it fixes our attention on the really 

 essential differences, and gives us an opportunity of making 

 more comprehensible, by simple relations in implements 

 familiar to us all, the complicated relations subsisting among 

 organisms. 



This is very striking as soon as we employ the concept of 

 the organ in the case of implements. As an example, let us 

 take a cane chair, the back legs of which are in one piece with 

 the back, which is fitted on to the seat ; and let us put the 

 following question to an anatomist and to a physiologist, " Is 

 this piece, composed of leg and back, an organ or not ? " 



