122 Analogy between Vegetables and Afiimals 



generated and maintained by the action of the nervous 

 system. 



Since, then, the temperature of the animal body is found to 

 be produced and supported by the functions of the nerves; 

 and since it is ascertained that plants possess the property of 

 always maintaining, under a great variety of circumstances, 

 a certain degree of temperature ; and since this property can- 

 not altogether be referred to any mechanical or chemical 

 process, we are bound, I think, to conclude that plants are 

 endued with a nervous structure. 



I have already stated that the higher classes of animal 

 beings are furnished with no less than five distinct sets of 

 nerves. The lower orders of animals possess a much fewer 

 number, and some of them have no nerves at all. Dr. Darwin, 

 from what he has advanced in his works, seems to infer that 

 vegetables possess as many classes of nerves as are found to 

 exist in animals of the most complicated and perfect struc- 

 ture. No one, I think, can agree with the opinion of this 

 fanciful but learned and amusing writer. It would be waste 

 of time to show that plants have neither nerves of percep- 

 tion nor of volition, nor nerves of sight, hearing, taste, or 

 smell. To endow them with these, would be to render them 

 at once intelligent beings. On an attentive consideration of 

 the subject, however, it appears to me that some vegetables 

 are endued with nerves of touch, with respiratory nerves, 

 with nerves of motion, and with ganglionic nerves. 



The sense of touch resides in the nerves distributed to the 

 skin. It is the only one which appears common to animals. 

 It has been ascertained that zoophytes, many of the mollus- 

 cous and articulated worms, and the larvae of various kinds of 

 insects, are not endued with vision ; and the sense of hearing 

 is found to be wanting in several species of insects and mol- 

 lusca. Many animals appear not to possess the faculty of 

 taste ; and it is doubtful whether there is an organ of smell 

 in cetaceous tribes, in amphibials, and in worms. There is 

 no animal, however, not even the most simple infusory ani- 

 malcule, in which the sense of touch does not exist. In con- 

 sequence of the sense of feeling being so universally present 

 in the animal kingdom, physiologists have considered it to be 

 the most simple and least elaborate state of the sensorial 

 power, or that subtle fluid which is secreted by the nervous 

 system, and constitutes the principle of sensation and motion. 

 There is likewise reason to conclude that from the material 

 of touch all the other senses are produced, by the operation 

 of peculiar and appropriate organs upon it. Thus, the optic 

 nerve converts it into vision, the auditory nerve modifies 



