58 Transactions Tennessee Academy of Science 



If, then, we find that plants and animals reveal essentially the 

 same fundamental structure, that they originate in the same way, 

 that their essential vital functions are the same, we naturally should 

 expect their behavior when exposed to abnormal conditions to be 

 subject at least to the same general laws. In other words, we 

 should expect striking analogies between animal and plant patho- 

 logical phenomena. 



When we attempt to compare the behavior of plants and animals 

 under pathological conditions, we must at the outset be very cautious 

 in assigning proper valuation to the great complexity of organiza- 

 tion in the higher animals and to the high degree of specialization 

 among their gross organs, their tissues and even their individual 

 cells. A modern machine gun is a much more efficient weapon of 

 offense or of defense than the old flintlock rifle used by Andrew 

 Jackson at New Orleans; but the modern weapon could be rendered 

 useless by a blow that would not in the least impair the perform- 

 ance of the simple and more primitive arm. Just one illustration 

 serves to emphasize this point. In the higher animals there is no 

 marked cellular response to the light stimulus except in a compara- 

 tively small group of cells contained in the visual apparatus which 

 we call the eye. In most plants the greater part of the cells of the 

 growing stems and leaves, and in some cases even the roots, are able 

 to perceive the light. In other words, light perception is generalized 

 in plant cells and loses in intensity. When from any pathological 

 condition, traumatic or otherwise, the animal's eyes are destroyed, 

 the whole body loses the power of response to the light stimulus. 

 The plant cannot have its "eyes" destroyed without the total de- 

 struction of its body. 



We are not surprised, therefore, to find a more striking ability 

 on the part of a plant to repair an injury or to regenerate or replace 

 an organ, and we find as we descend the animal scale this ability to 

 regenerate an amputated organ increases. It seems in a sense re- 

 markable that I have the third nail on one finger, it having been 

 twice regenerated after having been broken out. A salamander 

 would have grown out an entire arm or leg to replace the one 

 amjjutated. 



Thus we have in the plant scarcely a single vital organ in the 

 sense meant by that term in human physiology. If you amputate 

 the leaves, the stem and root survive and new leaves form. If vou 

 remove the root and place the stem under proper contlilions a new 



