392 Comparative Phijsioloyy. 



combinations of inorganic matter. Since the limited existence 

 of each individual wovild soon occasion the extinction of the 

 race, were no provision made for perpetuating it, each organism 

 has been endowed with the means of preparing a germ which, 

 when mature, may support an independent existence, execute 

 all the vital changes, and in its turn originate new beings by a 

 similar process. This function, common to all living beings, 

 is termed reproduction. There is a certain degree of antagonism 

 between the nutritive and reproductive functions. The mate- 

 rials of the reproductive are derived from the nutritive, and 

 dependent on it. Where the nutritive functions are particu- 

 larly active, as in algae, the reproductive is correspondingly 

 undeveloped; and, vice versa, in fungi the whole plant seems 

 made up of reproductive organs, and ceases to exist when the 

 germs are brought to maturity. The parts of the flower are 

 converted into leaves by an over-supply of nutriment ; and the 

 gardener who wishes to render a tree moi'e produ.ctive is 

 obliged to limit the supply of food by trenching round the 

 roots. The same antagonism may be Avitnessed in the animal 

 kingdom. During the period of rapid growth, when the energies 

 of the system ai-e concentrated uj)on the perfection of its indi- 

 vidual structure, the reproductive system remains dormant, and 

 is not aroused until the comparative inactivity of the nutritive 

 functions allows it to be exercised without injury to them. 

 The insect, in the larva condition, is wholly occupied with the 

 assimilation of food and increase of bulk. The same is the case, 

 more or less, with all young animals. In the imago, or perfect 

 insect, the fulfilment of the purposes of its reproductive system 

 appears to be the chief and only end of its being. In the adult 

 condition of the higher animals, it is always found that, as in 

 plants, an excessive activity of the nutritive function indis- 

 poses the system to the performance of the reproductive ; a 

 moderately fed population multiplying more rapidly than one 

 habituated to a plethoric condition. 



" The absorption of alimentary materials is the first in the 

 train of vital operations, and is common to plants and animals, 

 though somewhat differently performed in the two kingdoms. 

 The alimentary materials taken up by the absorbent system are 

 carried by the circulation into all parts of the fabric. This 

 movement is more necessary in the higher classes than in the 

 lower, where the absorbent surface is in more immediate relation 

 with the parts to be supplied. In animals, as in plants, this 

 function is entirely independent of the will, and in health un- 

 accompanied with consciousness. The muscular apparatus is 

 concerned in it only to harmonise it with the conditions of 

 animal existence ; and nervous agency merely brings it into 

 sympathy with other operations of the corporeal and mental 



