192 Comparative Physiology. 



rule ; in inorganic substances, permanence is the rule and change 

 the exception. In organised beings there are additional forces 

 to those of inorganic, resulting from properties nowhere else to 

 be found, and for which physical laws will by no means account. 

 The distinction between organic and inorganic bodies is com- 

 plete: the simplest of aerial flags, as the red snow, &c., as 

 well as the most simple animalcules, grow from a germ, increase, 

 reproduce, and die ; each, after its own kind, arranging their 

 particles in the same definite manner. The links between the 

 animal and vegetable kingdom are close and mutual ; but there 

 is a total want of resemblance in the mode of aggregation by 

 which minerals are held together." 



Some have held that it is difficult to distinguish between 

 infusorial animalcules, as nomades and vibrios, and inorganic 

 substances acted on by electricity. In the hardest animal 

 bodies particles have been found which have motion, and yet 

 are without life. Life, however, as explained above, is sepa- 

 rated from motion ; it is vague and absurd, he says, to infer from 

 these motions that all matter is possessed of vitality. 



The distinction between the vegetable and animal kingdom 

 is more difficult ; the above definition, however, of plants pos- 

 sessing individuality in each member or joint, and animals only 

 in the aggregate, is the most useful for practice. Sensibility 

 has been thought distinctive ; but some plants possess something 

 so like sensibility that it can hardly be distinguished from it, 

 and some of the lower animals, as hydatids, appear insensible to 

 stimuli. Plants have been said to live only on inorganic, and 

 animals only on organised, food ; but Sir Humphry Davy found 

 plants to thrive on sugar, gum, jelly, &c. ; and, as the depo- 

 sits of starch, &c., laid up for the food of young buds, germs, 

 &c., in the spring, are capable of affording nourishment, it 

 seems natural to infer that organised substances so minutely 

 divided as to be capable of absorption may be decomposed in 

 the same way and serve as nourishment. Miiller (vol. i. p. 4.) 

 says, " plants are nourished by organic substances in solution, 

 that have not wholly undergone decomj)osition, and also ge- 

 nerate organic compounds from inorganic." Dr. Lindley dis- 

 tinguishes between the two kingdoms, by plants being destitute 

 of locomotion, and being congeries of individuals ; which is the 

 most obvious, and perhaps the best, method of distinction. It 

 is true some animals divide spontaneously, and some are capable 

 of doing so artificially ; but they are so nearly allied to plants 

 as to have been sometimes classed among them. Some plants 

 also, as mushrooms and other cellular plants, will not propagate 

 by joints as other plants do, their multiplication being princi- 

 pally by ascini, thecce, spores, &c. The Monocotyledons also do 

 not divide so well into propagating joints as do the higher 



