164 THE INDrCTlONS OF BIOLOGY. 



certain other differentiated functions. Merchants, manu- 

 facturers, wholesale distributors of their several species, to- 

 gether with lawyers, bankers, &c., all employ clerks. In 

 clerks we have a specialized class dispersed through various 

 other classes ; and having its function fused with the differ- 

 ent functions of these various other classes. Similarly 

 commercial travellers, though having in one sense a 

 separate occupation, have in another sense an occupation 

 formuig part of each of the many occupations which it 

 aids. As it is here with the sociological division 



of labour, so is it with the physiological division of la- 

 bour above described. Just as we see in an advanced com- 

 munity, that while the magisterial, the clerical, the medical, 

 the legal, the manufacturing, and the commercial activities, 

 have grown distinct, they have yet their agencies mingled 

 together in every locality ; so in a developed organism, we 

 see that while the general functions of circulation, secretion, 

 absorption, excretion, contraction, excitation, &c., have be- 

 come differentiated, yet through the ramifications of the sys- 

 tems apportioned to them, they are closely combined with 

 each other in every organ. 



§ 60. The physiological division of labour, is usually not 

 carried so far as wholly to destroy the primary phj'siological 

 community of labour. As in societies the adaptation of special 

 classes to special duties, does not entirelj'' disable these classes 

 from performing each others' duties on an emergency ; so in 

 organisms, tissues and structures that have become fitted to 

 the particular offices they have ordinarily to discharge, often 

 remain partially able to discharge other offices. It has been 

 pointed out by Dr Carpenter, that " in cases where the differ 

 ent functions are highly specialized, the general structure 

 retains, more or less, the primitive community of functi(tn 

 which originally characterized it." A few instances will 

 bring home this generalization. 



The roots and leaves of plants are widely different!- 



